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  • JavaScript inheritance

    - by Tower
    Hi, Douglas Crockford seems to like the following inheritance approach: if (typeof Object.create !== 'function') { Object.create = function (o) { function F() {} F.prototype = o; return new F(); }; } newObject = Object.create(oldObject); It looks OK to me, but how does it differ from John Resig's simple inheritance approach? Basically it goes down to newObject = Object.create(oldObject); versus newObject = Object.extend(); And I am interested in theories. Implementation wise there does not seem to be much difference.

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  • Is block style really this important?

    - by Jack Roscoe
    I just watched a video of Douglas Crockford's presentation about his 2009 book JavaScript: The Good Parts. In the video, he explains that the following block is dangerous because it produces silent errors: return { ok: false }; And that it should actually be written like this (emphasising that although seemingly identical the behavioural difference is crucial): return { ok: false }; You can see his comments around 32 minutes into the video here: http://www.youtube.com/watch?v=hQVTIJBZook&feature=player_embedded#!&start=1920 I have not heard this before, and was wondering if this rule still applies or if this requirement in syntax has been overcome by JavaScript developments since this statement was made. I found this very interesting as I have NOT been writing my code this way, and wanted to check that this information was not out of date.

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  • Javascript Prototyping Question

    - by Nick Lowman
    I'm just reading about Prototypes in JavaScript and Douglas Crockford offers and excellent way to select a new objects prototype but can anyone explain (below) why obj01's type equals 'object' when I pass it in function as it's prototype? if (typeof Object.beget !== 'function') { Object.beget = function (o) { console.log(typeof o);//function var F = function () {}; F.prototype = o; console.log(typeof F);//function return new F(); }; } var func01 = function(){}; var obj01 = Object.beget(func01); console.log(typeof obj01);//object console.log(typeof obj01.prototype);//object I thought it would be console.log(typeof obj01);//function console.log(typeof obj01.prototype);//function

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  • Storing DOM reference elements in Javascript array

    - by webzide
    Dear experts, I was trying to dynamically generate DOM elements using JS. I read from Douglas Crockford's book that DOM is very very poorly structured. Anyways, I would like to create a number of DIVISION elements and store the reference into an array so it could be accessed later. Here's the code for(i=0;i<3;i++){ var div=document.body.appendChild(document.createElement("div")); var arr=new Array(); arr.push(div); } Somehow this would not work..... There is only 1 div element created. When I use the arr.length to test the code there is only 1 element in the array. Is there another way to accomplish this. THanks in advance

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  • Is there any data missing?

    - by smwikipedia
    Hi experts, Here is some code quoted from Douglas.E.Comer's < Computer Networks and Internets 4th edition. This program will send back any data it received. ... while((len = recv(conn, buff, BUFFERSIZE,0)) >0) // receive data send(conn, buff, len, 0); // send it back ... I am wondering, what if some data arrived when the code is executing in send(..) function, will it miss that data? Because the recv() function is not being executed. If no data is missed, where is the data kept? And by whom? Thanks...

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  • Advice Please: SQL Server Identity vs Unique Identifier keys when using Entity Framework

    - by c.batt
    I'm in the process of designing a fairly complex system. One of our primary concerns is supporting SQL Server peer-to-peer replication. The idea is to support several geographically separated nodes. A secondary concern has been using a modern ORM in the middle tier. Our first choice has always been Entity Framework, mainly because the developers like to work with it. (They love the LiNQ support.) So here's the problem: With peer-to-peer replication in mind, I settled on using uniqueidentifier with a default value of newsequentialid() for the primary key of every table. This seemed to provide a good balance between avoiding key collisions and reducing index fragmentation. However, it turns out that the current version of Entity Framework has a very strange limitation: if an entity's key column is a uniqueidentifier (GUID) then it cannot be configured to use the default value (newsequentialid()) provided by the database. The application layer must generate the GUID and populate the key value. So here's the debate: abandon Entity Framework and use another ORM: use NHibernate and give up LiNQ support use linq2sql and give up future support (not to mention get bound to SQL Server on DB) abandon GUIDs and go with another PK strategy devise a method to generate sequential GUIDs (COMBs?) at the application layer I'm leaning towards option 1 with linq2sql (my developers really like linq2[stuff]) and 3. That's mainly because I'm somewhat ignorant of alternate key strategies that support the replication scheme we're aiming for while also keeping things sane from a developer's perspective. Any insight or opinion would be greatly appreciated.

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  • Was I wrong about JavaScript?

    - by jboyer
    Yes, I was. Recently, I’ve taken a good hard look at JavaScript. I’ve used it before but mostly in the capacity of web design. Using JQuery to make your web page do cool stuff is different than really creating a JavaScript application using all of the language constructs. What I’m finding as I use it more is that I may have been wrong about my assumptions about it. Let me explain.   I enjoyed doing cool stuff with JQuery but the limited experience with JavaScript as a language coupled with the bad things that I heard about it led me to not have any real interest in it. However, JavaScript is ubiquitous on the web and if I want to do any web development, which I do, I need to learn it. So here I am, diving deep into the language with the help of the JavaScript Fundamentals training course at Pluralsight (great training for a low price) and the JavaScript: The Good Parts book by Douglas Crockford.   Now, there are certainly parts of JavaScript that are bad. I think these are well known by any developer that uses it. The parts that I feel are especially egregious are the following: The global object null vs. undefined truthy and falsy limited (nearly nonexistent) scoping ‘==’ and ‘===’ (I just don’t get the reason for coercion)   However, what I am finding hiding under the covers of the bad things is a good language. I am finding that I am legitimately enjoying JavaScript. This I was not expecting. I’m not going to go into a huge dissertation on what I like about it, but some things include: Object literal notation dynamic typing functional style (JavaScript: The Good Parts describes it as LISP in C clothing) JSON (better than XML) There are parts of JavaScript that seem strange to OOP developers like myself. However, just because it is different or seems strange does not mean it is bad. Some differences are quite interesting and useful.   I feel that it is important for developers to challenge their assumptions and also to be able to admit when they are wrong on a topic. Many different situations can arise that lead to this, such as choosing the wrong technology for a problem’s solution, misunderstanding the requirements, etc. I decided to challenge my assumptions about JavaScript instead of moving straight into CoffeeScript or Dart. After exploring it, I find that I am beginning to enjoy it the more I use it. As long as there are those like Crockford to help guide me in the right way to code in JavaScript, I can create elegant and efficient solutions to problems and add another ‘arrow’ to the ‘quiver’, so to speak. I do still intend to learn CoffeeScript to see what the hub-bub is about, but now I no longer have to be afraid of JavaScript as a legitimate programming language.   Has something similar ever happened to you? Tell me about it in the comments below.

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  • TCP Handshake and port numbers

    - by Guido
    (I have a question about the TCP handshake and how port numbers are assigned, if this does not belong here, let me know.) Hi, I'm studying TCP/IP from the book "Internetworking with TCP/IP" by Douglas Comer. In the TCP chapter it mentions that TCP defines an "endpoint" as a pair (IP address, port number), and a connection is defined by two endpoints. This has a few implications, such as, a local TCP port could be in several connections at once, as long as there are no two from the same IP and the same remote port. This also means that the amount of established connections is almost limitless (2^16 for every IPv4 address. 2^48 in total). Now, in class, I was told that when one connects to a listening port, both sides agree on a different port to use, so the communication can happen and the listener socket remains free. This was also my belief before reading the book. Now I feel like I should obviously trust the book (It's Comer!), but is there any truth to the other explanation? Thanks

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  • Agile Database Techniques: Effective Strategies for the Agile Software Developer – book review

    - by DigiMortal
       Agile development expects mind shift and developers are not the only ones who must be agile. Every chain is as strong as it’s weakest link and same goes also for development teams. Agile Database Techniques: Effective Strategies for the Agile Software Developer by Scott W. Ambler is book that calls also data professionals to be part of agile development. Often are DBA-s in situation where they are not part of application development and later they have to survive large set of applications that all use databases different way. Of course, only some of these applications are not problematic when looking what database server has to do to serve them. I have seen many applications that rape database servers because developers have no clue what is going on in database (~3K queries to database per web application request – have you seen something like this? I have…) Agile Database Techniques covers some object and database design technologies and gives suggestions to development teams about topics they need help or assistance by DBA-s. The book is also good reading for DBA-s who usually are not very strong in object technologies. You can take this book as bridge between these two worlds. I think teams that build object applications that use databases should buy this book and try at least one or two projects out with Ambler’s suggestions. Table of contents Foreword by Jon Kern. Foreword by Douglas K. Barry. Acknowledgments. Introduction. About the Author. Part One: Setting the Foundation. Chapter 1: The Agile Data Method. Chapter 2: From Use Cases to Databases — Real-World UML. Chapter 3: Data Modeling 101. Chapter 4: Data Normalization. Chapter 5: Class Normalization. Chapter 6: Relational Database Technology, Like It or Not. Chapter 7: The Object-Relational Impedance Mismatch. Chapter 8: Legacy Databases — Everything You Need to Know But Are Afraid to Deal With. Part Two: Evolutionary Database Development. Chapter 9: Vive L’ Évolution. Chapter 10: Agile Model-Driven Development (AMDD). Chapter 11: Test-Driven Development (TDD). Chapter 12: Database Refactoring. Chapter 13: Database Encapsulation Strategies. Chapter 14: Mapping Objects to Relational Databases. Chapter 15: Performance Tuning. Chapter 16: Tools for Evolutionary Database Development. Part Three: Practical Data-Oriented Development Techniques. Chapter 17: Implementing Concurrency Control. Chapter 18: Finding Objects in Relational Databases. Chapter 19: Implementing Referential Integrity and Shared Business Logic. Chapter 20: Implementing Security Access Control. Chapter 21: Implementing Reports. Chapter 22: Realistic XML. Part Four: Adopting Agile Database Techniques. Chapter 23: How You Can Become Agile. Chapter 24: Bringing Agility into Your Organization. Appendix: Database Refactoring Catalog. References and Suggested Reading. Index.

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  • #MIX Day 2 Keynote: Put the Phone Down and Listen

    - by andrewbrust
    MIX day 1’s keynote was all about Windows Phone 7 (WP7).  MIX day 2’s was a reminder that Microsoft has much more going on than a new mobile platform.  Steven Sinofsky, Scott Guthrie, Doug Purdy and others showed us lots of other good things coming from Microsoft, mostly in the developer stack, that we certainly shouldn’t overlook.  These included the forthcoming IE9, its new JavaScript compiling engine and support for HTML 5 that takes full advantage of the local PC resources, including the Graphics Processing Unit.  The announcements also included important additions to ASP.NET (and one subtraction, in the form of lighter-weight ViewState technology) including almost-obsessive jQuery support.  That support is so good that John Resig, creator of the jQuery project, came on stage to tell us so.  Then Scott Guthrie told us that Microsoft would be contributing code to Open Source jQuery project. This is not your father’s Microsoft, it would seem. But to me, the crown jewel in today’s keynote were the numerous announcements around the Open Data Protocol (OData).  OData is nothing more than the protocol side of “Astoria” (now known as WCF Data Services, and until recently called ADO.NET Data Services) separated out and opened up as a platform-neutral standard.  The 2009 Professional Developers Conference (PDC) was Microsoft’s vehicle for first announcing OData, as well as project “Dallas,” an Azure-based cloud platform for publishing commercial OData feeds.  And we had already known about “bridges” for Astoria (and thus OData) for PHP and Java.  We also knew that PowerPivot, Microsoft’s forthcoming self-service BI plug-in for Excel 2010, will consume OData feeds and then facilitate drill-down analysis of their data.  And we recently found out that SQL Reporting Services reports (in the forthcoming SQL Server 2008 R2) and SharePoint 2010 lists will be consumable in OData format as well. So what was left to announce?  How about OData clients for Palm webOS and Apple iPhone/Objective C?  How about the release to Open Source of .NET’s OData client?  Or the ability to publish any SQL Azure database as an OData service by simply checking a checkbox at deployment?  Maybe even a Silverlight tool (code-named “Houston”) to create SQL Azure databases (and then publish them as OData) right in the browser?  And what if you you could get at NetFlix’s entire catalog in OData format?  You can – just go to http://odata.netflix.com/Catalog/ and see for yourself.  Douglas Purdy, who made these announcements said “we want OData to work on as many devices and platforms as possible.”  After all the cross-platform OData announcements made in about a half year’s time, it’s hard to dispute this. When Microsoft plays the data card, and plays it well, watch out, because data programmability is the company’s heritage.  I’ll be discussing OData at length in my April Redmond Review column.  I wrote that column two weeks ago, and was convinced then that OData was a big deal. Today upped the ante even more.  And following the Windows Phone 7 euphoria of yesterday was, I think, smart timing.  The phone, if it’s successful, will be because it’s a good developer platform play.  And developer platforms (as well as their creators) are most successful when they have a good data strategy.  OData is very Silverlight-friendly, and that means it’s WP7-friendly too.  Phone plus service-oriented data is a one-two punch.  A phone platform without data would have been a phone with no signal.

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  • Why don't we just fix Javascript?

    - by Jan Meyer
    Javascript sucks because of a few fatalities well pointed out by Douglas Crockford. We talk a lot about it. But the point here is, why we don't fix it? Coffeescript of course does that and a lot more. But the question here is another: if we provide a webservice that can convert one version of Javascript to the next, and so on, we can keep the language up to date. Such a conversion allows old code to run, albeit with an ever-increasing startup delay, as newer browsers convert old code to the new syntax. To avoid that delay, the site only needs to take the output of the code-transform and paste it in! The effort has immediate benefits for those businesses interested in the results. The rest can sleep tight: their code will continue to run. If we provide backward code-transformation also, then elder browsers can also run ANY new code! Migration scripts should be created by those that make changes to a language. Today they don't, which is in itself a fundamental omission! It should be am obvious part of their job to provide them, as their job isn't really done without them. The onus of making it work should be on them. With this system Any site will be able to run in Any browser, but new code will run best on the newest browsers. This way we reap the benefit of an up-to-date and productive development environment, where today we suffer, supposedly because of yesterday. This is a misconception. We are all trapped in committee-thinking, and we drag along things that only worsen our performance over time! We cause an ever increasing complexity that is hard to underestimate. Javascript is easily fixed. The fact is we don't. As an example, I have seen Patrick Michaud tackle the migration problem in PmWiki. It included forward migration scripts. Whenever syntax changes were made, a migration script was added to transform pages to the new syntax. As far as I know, ALL migrations have worked flawlessly. In other words, we don't tackle the migration problem, we just drag it along. We are incompetent! And why is that? Because technically incompetent people feel they must decide for us. Because they are incompetent, fear rules them. They are obnoxiously conservative, and we suffer the consequence of bad leadership. But the competent don't need to play by the same rules. They can (and must) change them. They are the path forward. It is about time to leave the past behind, and pursue the leanest meanest, no, eternal functionality. That would in and of itself revolutionize programming. So, why don't we stop whining and fix programming? Begin with Javascript and change the world. Even if the browser doesn't hook into this system, coders could. So language updaters should take it upon them to provide migration scripts. Once they exist, browsers may take advantage of them.

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  • Get to Know a Candidate (3 of 25): Virgil Goode&ndash;Constitution Party

    - by Brian Lanham
    DISCLAIMER: This is not a post about “Romney” or “Obama”. This is not a post for whom I am voting. Information sourced for Wikipedia. Meet Virgil Goode of the Constitution Party Goode was served as a Republican member of the United States House of Representatives from 1997 to 2009. He represented the 5th congressional district of Virginia. Goode was born in Richmond, Virginia, the son of Alice Clara (née Besecker) and Virgil Hamlin Goode. He has spent most of his life in Rocky Mount. Goode graduated with a B.A. from the University of Richmond (Phi Beta Kappa) and with a J.D. from the University of Virginia School of Law. He also is a member of Lambda Chi Alpha Fraternity and served in the Army National Guard from 1969 to 1975. Goode grew up as a Democrat. He entered politics soon after graduating from law school. At the age of 27, he won a special election to the state Senate from a Southside district as an independent after the death of the Democratic incumbent. One of his major campaign focuses at the time was advocacy for the Equal Rights Amendment. Soon after being elected, he joined the Democrats. Goode wore his party ties very loosely. He became famous for his support of the tobacco industry, expressing his fear that "his elderly mother would be denied 'the one last pleasure' of smoking a cigarette on her hospital deathbed." He was an ardent defender of gun rights while being an enthusiastic supporter of L. Douglas Wilder, who later became the first elected black governor in the history of the United States. At the Democratic Party's state political convention in 1985, Goode nominated Wilder for lieutenant governor. However, while governor, Wilder cracked down on the sale of guns in the state. After the 1995 elections resulted in a 20–20 split between Democrats and Republicans in the State Senate, Goode seriously considered voting with the Republicans on organizing the chamber. Had he done so, the State Senate would have been under Republican control for the first time since Reconstruction (the Republicans ultimately won control outright in 1999). Goode's actions at the time "forced his party to share power with Republican lawmakers in the state legislature," which further upset the Democratic Party. Goode is on the ballot in CA, FL, ID, IO, LA, MI, MN, MS, MI, NJ, NM, NY, NV, ND, OH, SC, SD, TN, UT, VA, WA, WI, WY.  He is a write-in candidate in CA, CT, DC, GA, IL, IN, ME, MD, MA, MO, NC, TX, VT, WV Constitution Party This party was founded as the “U.S. Taxpayers’ Party” and considers itself conservative. The party's platform is predicated on the principles of the nation's founding documents. The party puts a large focus on immigration, calling for stricter penalties towards illegal immigrants and a moratorium on legal immigration until all federal subsidies to immigrants are discontinued.The party absorbed the American Independent Party, originally founded for George Wallace's 1968 presidential campaign. The American Independent Party of California has been an affiliate of the Constitution Party since its founding; however, current party leadership is disputed and the issue is in court to resolve this conflict. The Constitution Party has some substantial support from the Christian Right and in 2010 achieved major party status in Colorado. Learn more about Virgil Goode and Constitution Party on Wikipedia.

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  • Using HTML5 Today part 3&ndash; Using Polyfills

    - by Steve Albers
    Shims helps when adding semantic tags to older IE browsers, but there is a huge range of other new HTML5 features that having varying support on browsers.  Polyfills are JavaScript code and/or browser plug-ins that can provide older or less featured browsers with API support.  The best polyfills will detect the whether the current browser has native support, and only adds the functionality if necessary.  The Douglas Crockford JSON2.js library is an example of this approach: if the browser already supports the JSON object, nothing changes.  If JSON is not available, the library adds a JSON property in the global object. This approach provides some big benefits: It lets you add great new HTML5 features to your web sites sooner. It lets the developer focus on writing to the up-and-coming standard rather than proprietary APIs. Where most one-off legacy code fixes tends to break down over time, well done polyfills will stop executing over time (as customer browsers natively support the feature) meaning polyfill code may not need to be tested against new browsers since they will execute the native methods instead. Your should also remember that Polyfills represent an entirely separate code path (and sometimes plug-in) that requires testing for support.  Also Polyfills tend to run on older browsers, which often have slower JavaScript performance.  As a result you might find that performance on older browsers is not comparable. When looking for Polyfills you can start by checking the Modernizr GitHub wiki or the HTML5 Please site. For an example of a polyfill consider a page that writes a few geometric shapes on a <canvas> <script src="jquery-1.7.1.min.js"><script> <script> $(document).ready(function () { drawCanvas(); }); function drawCanvas() { var context = $("canvas")[0].getContext('2d'); //background context.fillStyle = "#8B0000"; context.fillRect(5, 5, 300, 100); // emptybox context.strokeStyle = "#B0C4DE"; context.lineWidth = 4; context.strokeRect(20, 15, 80, 80); // circle context.arc(160, 55, 40, 0, Math.PI * 2, false); context.fillStyle = "#4B0082"; context.fill(); </script>   The result is a simple static canvas with a box & a circle:   …to enable this functionality on a pre-canvas browser we can find a polyfill.  A check on html5please.com references  FlashCanvas.  Pull down the zip and extract the files (flashcanvas.js, flash10canvas.swf, etc) to a directory on your site.  Then based on the documentation you need to add a single line to your original HTML file: <!--[if lt IE 9]><script src="flashcanvas.js"></script><![endif]—> …and you have canvas functionality!  The IE conditional comments ensure that the library is only loaded in browsers where it is useful, improving page load & processing time. Like all Polyfills, you should test to verify the functionality matches your expectations across browsers you need to support.  For instance the Flash Canvas home page advertises 70% support of HTML5 Canvas spec tests.

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  • Top-Rated JavaScript Blogs

    - by Andreas Grech
    I am currently trying to find some blogs that talk (almost solely) on the JavaScript Language, and this is due to the fact that most of the time, bloggers with real life experience at work or at home development can explain more clearly and concisely certain quirks and hidden features than most 'Official Language Specifications' Below find a list of blogs that are JavaScript based (will update the list as more answers flow in): DHTML Kitchen, by Garrett Smith Robert's Talk, by Robert Nyman EJohn, by John Resig (of jQuery) Crockford's JavaScript Page, by Douglas Crockford Dean.edwards.name, by Dean Edwards Ajaxian, by various (@Martin) The JavaScript Weblog, by various SitePoint's JavaScript and CSS Page, by various AjaxBlog, by various Eric Lippert's Blog, by Eric Lippert (talks about JScript and JScript.Net) Web Bug Track, by various (@scunliffe) The Strange Zen Of JavaScript , by Scott Andrew Alex Russell (of Dojo) (@Eran Galperin) Ariel Flesler (@Eran Galperin) Nihilogic, by Jacob Seidelin (@llimllib) Peter's Blog, by Peter Michaux (@Borgar) Flagrant Badassery, by Steve Levithan (@Borgar) ./with Imagination, by Dustin Diaz (@Borgar) HedgerWow (@Borgar) Dreaming in Javascript, by Nosredna spudly.shuoink.com, by Stephen Sorensen Yahoo! User Interface Blog, by various (@Borgar) remy sharp's b:log, by Remy Sharp (@Borgar) JScript Blog, by the JScript Team (@Borgar) Dmitry Baranovskiy’s Web Log, by Dmitry Baranovskiy James Padolsey's Blog (@Kenny Eliasson) Perfection Kills; Exploring JavaScript by example, by Juriy Zaytsev DailyJS (@Ric) NCZOnline (@Kenny Eliasson), by Nicholas C. Zakas Which top-rated blogs am I currently missing from the above list, that you think should be imperative to any JavaScript developer to read (and follow) concurrently?

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  • Javascript functional inheritance with prototypes

    - by cdmckay
    In Douglas Crockford's JavaScript: The Good Parts he recommends that we use functional inheritance. Here's an example: var mammal = function(spec, my) { var that = {}; my = my || {}; // Protected my.clearThroat = function() { return "Ahem"; }; that.getName = function() { return spec.name; }; that.says = function() { return my.clearThroat() + ' ' + spec.saying || ''; }; return that; } var cat = function(spec, my) { var that = {}; my = my || {}; spec.saying = spec.saying || 'meow'; that = mammal(spec, my); that.purr = function() { return my.clearThroat() + " purr"; }; that.getName = function() { return that.says() + ' ' + spec.name + ' ' + that.says(); }; return that; }; var kitty = cat({name: "Fluffy"}); The main issue I have with this is that every time I make a mammal or cat the JavaScript interpreter has to re-compile all the functions in it. That is, you don't get to share the code between instances. My question is: how do I make this code more efficient? For example, if I was making thousands of cat objects, what is the best way to modify this pattern to take advantage of the prototype object?

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  • Executes a function until it returns a nil, collecting its values into a list

    - by Baldur
    I got this idea from XKCD's Hofstadter comic; what's the best way to create a conditional loop in (any) Lisp dialect that executes a function until it returns NIL at which time it collects the returned values into a list. For those who haven't seen the joke, it's goes that Douglas Hofstadter's “eight-word” autobiography consists of only six words: “I'm So Meta, Even This Acronym” containing continuation of the joke: (some odd meta-paraprosdokian?) “Is Meta” — the joke being that the autobiography is actually “I'm So Meta, Even This Acronym Is Meta”. But why not go deeper? Assume the acronymizing function META that creates an acronym from a string and splits it into words, returns NIL if the string contains but one word: (meta "I'm So Meta, Even This Acronym") ? "Is Meta" (meta (meta "I'm So Meta, Even This Acronym")) ? "Im" (meta (meta (meta "I'm So Meta, Even This Acronym"))) ? NIL (meta "GNU is Not UNIX") ? "GNU" (meta (meta "GNU is Not UNIX")) ? NIL Now I'm looking for how to implement a function so that: (so-function #'meta "I'm So Meta, Even This Acronym") ? ("I'm So Meta, Even This Acronym" "Is Meta" "Im") (so-function #'meta "GNU is Not Unix") ? ("GNU is Not Unix" "GNU") What's the best way of doing this?

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  • Using "Object.create" instead of "new"

    - by Graham King
    Javascript 1.9.3 / ECMAScript 5 introduces Object.create, which Douglas Crockford amongst others has been advocating for a long time. How do I replace new in the code below with Object.create? var UserA = function(nameParam) { this.id = MY_GLOBAL.nextId(); this.name = nameParam; } UserA.prototype.sayHello = function() { console.log('Hello '+ this.name); } var bob = new UserA('bob'); bob.sayHello(); (Assume MY_GLOBAL.nextId exists). The best I can come up with is: var userB = { init: function(nameParam) { this.id = MY_GLOBAL.nextId(); this.name = nameParam; }, sayHello: function() { console.log('Hello '+ this.name); } }; var bob = Object.create(userB); bob.init('Bob'); bob.sayHello(); There doesn't seem to be any advantage, so I think I'm not getting it. I'm probably being too neo-classical. How should I use Object.create to create user 'bob'?

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  • Intelligent web features, algorithms (people you may follow, similar to you ...)

    - by hilal
    I have 3 main questions about the algorithms in intelligent web (web 2.0) Here the book I'm reading http://www.amazon.com/Algorithms-Intelligent-Web-Haralambos-Marmanis/dp/1933988665 and I want to learn the algorithms in deeper 1. People You may follow (Twitter) How can one determine the nearest result to my requests ? Data mining? which algorithms? 2. How you’re connected feature (Linkedin) Simply algorithm works like that. It draws the path between two nodes let say between Me and the other person is C. Me - A, B - A connections - C . It is not any brute force algorithms or any other like graph algorithms :) 3. Similar to you (Twitter, Facebook) This algorithms is similar to 1. Does it simply work the max(count) friend in common (facebook) or the max(count) follower in Twitter? or any other algorithms they implement? I think the second part is true because running the loop dict{count, person} for person in contacts: dict.add(count(common(person))) return dict(max) is a silly act in every refreshing page. 4. Did you mean (Google) I know that they may implement it with phonetic algorithm http://en.wikipedia.org/wiki/Phonetic_algorithm simply soundex http://en.wikipedia.org/wiki/Soundex and here is the Google VP of Engineering and CIO Douglas Merrill speak http://www.youtube.com/watch?v=syKY8CrHkck#t=22m03s What about first 3 questions? Any ideas are welcome ! Thanks

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  • Should I be worried about a ReDOS attack?

    - by PeeHaa
    Can the following code be use to ReDOS attack my site? Or will it just be ended when the max_execution_time is exceeded or is it a problem of the past? I use the following code to validate emailaddresses on my sites (by Douglas Lovell): function validate_email($email) { $isValid = true; $atIndex = strrpos($email, "@"); if (is_bool($atIndex) && !$atIndex) { $isValid = false; } else { $domain = substr($email, $atIndex+1); $local = substr($email, 0, $atIndex); $localLen = strlen($local); $domainLen = strlen($domain); if ($localLen < 1 || $localLen > 64) { // local part length exceeded $isValid = false; } else if ($domainLen < 1 || $domainLen > 255) { // domain part length exceeded $isValid = false; } else if ($local[0] == '.' || $local[$localLen-1] == '.') { // local part starts or ends with '.' $isValid = false; } else if (preg_match('/\\.\\./', $local)) { // local part has two consecutive dots $isValid = false; } else if (!preg_match('/^[A-Za-z0-9\\-\\.]+$/', $domain)) { // character not valid in domain part $isValid = false; } else if (preg_match('/\\.\\./', $domain)) { // domain part has two consecutive dots $isValid = false; } else if(!preg_match('/^(\\\\.|[A-Za-z0-9!#%&`_=\\/$\'*+?^{}|~.-])+$/', str_replace("\\\\","",$local))) { // character not valid in local part unless // local part is quoted if (!preg_match('/^"(\\\\"|[^"])+"$/', str_replace("\\\\","",$local))) { $isValid = false; } } if ($isValid && !(checkdnsrr($domain,"MX") || checkdnsrr($domain,"A"))) { // domain not found in DNS $isValid = false; } } return $isValid; }

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  • How to have an iCalendar (RFC 2445) repeat YEARLY with duration

    - by Todd Brooks
    I have been unsuccessful in formulating a RRULE that would allow an event as shown below: Repeats YEARLY, from first Sunday of April to last day of May, occuring on Monday, Wednesday and Friday, until forever. FREQ=YEARLY;BYMONTH=4;BYDAY=SU (gives me the first Sunday of April repeating yearly) and FREQ=YEARLY;BYMONTH=5;BYMONTHDAY=-1 (gives me the last day of May repeating yearly) But I can't figure out how to have the event repeat yearly between those dates for Monday, Wednesday and Friday. Suggestions? Update: Comments don't have enough space to respond to Chris' answer, so I am editing the question with further information. Unfortunately, no. I don't know if it is the DDay.iCal library I'm using, or what, but that doesn't work either. I've found that the date start can't be an ordinal date (first Sunday, etc.)..it has to be a specific date, which makes it difficult for my requirements. Even using multiple RRULE's it doesn't seem to work: BEGIN:VCALENDAR VERSION:2.0 PRODID:-//DDay.iCal//NONSGML ddaysoftware.com//EN BEGIN:VEVENT CREATED:20090717T033307Z DTSTAMP:20090717T033307Z DTSTART:20090101T000000 RRULE:FREQ=YEARLY;WKST=SU;BYDAY=MO,WE,FR;BYMONTH=4,5 RRULE:FREQ=YEARLY;WKST=SU;BYDAY=1SU;BYMONTH=4 RRULE:FREQ=YEARLY;WKST=SU;BYMONTH=5;BYMONTHDAY=-1 SEQUENCE:0 UID:352ed9d4-04d0-4f06-a094-fab7165e5c74 END:VEVENT END:VCALENDAR That looks right on the face (I'm even starting the event on 1/1/2009), but when I start testing whether certain days are valid, I get incorrect results. For example, 4/1/2009 12:00:00 AM = True // Should be False 4/6/2009 12:00:00 AM = True 4/7/2009 12:00:00 AM = False 4/8/2009 12:00:00 AM = True 5/1/2009 12:00:00 AM = True 5/2/2009 12:00:00 AM = False 5/29/2009 12:00:00 AM = True 5/31/2009 12:00:00 AM = True // Should be False 6/1/2009 12:00:00 AM = False I'm using Douglas Day's DDay.iCal software, but I don't think it is a bug in that library. I think this might be a limitation in iCalendar (RFC 2445). Thoughts?

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  • WHY JSLint complains: "someFunction() was used before it was defined"?

    - by 7hi4g0
    Searching for the JSLint error "was used before it was defined" i've found these: JSLint: Using a function before it's defined error Function was used before it was defined - JSLint JSLint: was used before it was defined jsLint error: “somefunction() was used before it was defined” jslint - Should we tolerate misordered definitions? Problem None of those answers WHY the error is shown. Elaboration According to the ECMA-262 Specification functions are evaluated before execution starts, hence all functions declared using the function keyword are available to all the code idenpendent of the place they were declared (assuming they are acessible on that scope). This is otherwise known as hoisting. Douglas Crockford seems to think it is better to declare every function before the code that uses it regardless of the hoisting effect. According to StackOverflowNewbie in his question, this raises some code organization problems. Not to mention some people, like me, prefer to declare their functions underneath the main/init code. On those questions there are some ways to avoid or fix the error, such as using function expressions vs function declarations. But none of them showed me the reason of the error. Not even Crockford's site. Question(s) Why is it an error to call a function before the declaration, even if it was declared using the function keyword? Is it better to use function expressions instead of function declaration in the JSLint context? If one is preferred, why? Note Not looking for answers like: Crockford is a tyrant Is just Crockford's opinion Thank you :*

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  • Copying Columns from Grid to Clipboard in SQL Developer

    - by thatjeffsmith
    There are several ways to get data from a query or a table|view to the clipboard. You know the tried and true, copy and paste. But what if you only want one or more columns, not every column? There are several ways to do this, let’s see if we can’t identify all of them. Write your query to only include the data you want Obvious? Yes. Needed to be said? Definitely. The best tuning tip is to only ask for the data you need, only when you absolutely need it. But let’s look at a few more practical ways to do this. Hide the unwanted columns Mouse right click on an column header. In the context menu, select ‘Columns.’ Hide the columns you don’t want. Copy and paste. WYSIWYG Grids, Hide Columns and Filter Rows Mouse select the columns Obvious, but a bit painful. For a very large dataset, you’ll be holding down the Shift and PageDown buttons – but it works. Remember to use Ctrl+Shift+C to get the column headers with the data. Use the Export Wizard This used to be called ‘Unload’ – agreed, not a great name. So, we changed it. In a grid, right mouse click on the data, and on the context menu, select ‘Export…’ Select your format – I suggest ‘delimited’ or ‘fixed’ for copying data to the clipboard. You can export to the clipboard, yes you can! Click ‘Next.’ Click in the Columns dialog, and choose the columns you want copied. Trim the columns you don't want copied Click ‘Finish.’ Alt or Ctrl tab to your window or application of choice. And Paste! "FIRST_NAME" "LAST_NAME" "Donald" "OConnell" "Douglas" "Grant" "Jennifer" "Whalen" "Pat" "Fay" "Susan" "Mavris" "William" "Gietz" "Alexander" "Hunold" "Bruce" "Ernst" "David" "Austin" "Valli" "Pataballa" "Diana" "Lorentz" "Daniel" "Faviet" "John" "Chen" "Ismael" "Sciarra" "Jose Manuel" "Urman" "Luis" "Popp" "Alexander" "Khoo" "Shelli" "Baida" "Sigal" "Tobias" "Guy" "Himuro" "Karen" "Colmenares" "Matthew" "Weiss" "Adam" "Fripp" "Payam" "Kaufling" "Shanta" "Vollman" "Kevin" "Mourgos" "Julia" "Nayer" "Irene" "Mikkilineni" ... There’s probably at least 2 or 3 more ways, but… But, try these and let me know how we can improve things. I’ve already gotten a request to be able to include the SQL text used to populate the dataset on the the copy to clipboard, and it’s now on our to-do list

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  • A C# implementation of the CallStream pattern

    - by Bertrand Le Roy
    Dusan published this interesting post a couple of weeks ago about a novel JavaScript chaining pattern: http://dbj.org/dbj/?p=514 It’s similar to many existing patterns, but the syntax is extraordinarily terse and it provides a new form of friction-free, plugin-less extensibility mechanism. Here’s a JavaScript example from Dusan’s post: CallStream("#container") (find, "div") (attr, "A", 1) (css, "color", "#fff") (logger); The interesting thing here is that the functions that are being passed as the first argument are arbitrary, they don’t need to be declared as plug-ins. Compare that with a rough jQuery equivalent that could look something like this: $.fn.logger = function () { /* ... */ } $("selector") .find("div") .attr("A", 1) .css("color", "#fff") .logger(); There is also the “each” method in jQuery that achieves something similar, but its syntax is a little more verbose. Of course, that this pattern can be expressed so easily in JavaScript owes everything to the extraordinary way functions are treated in that language, something Douglas Crockford called “the very best part of JavaScript”. One of the first things I thought while reading Dusan’s post was how I could adapt that to C#. After all, with Lambdas and delegates, C# also has its first-class functions. And sure enough, it works really really well. After about ten minutes, I was able to write this: CallStreamFactory.CallStream (p => Console.WriteLine("Yay!")) (Dump, DateTime.Now) (DumpFooAndBar, new { Foo = 42, Bar = "the answer" }) (p => Console.ReadKey()); Where the Dump function is: public static void Dump(object options) { Console.WriteLine(options.ToString()); } And DumpFooAndBar is: public static void DumpFooAndBar(dynamic options) { Console.WriteLine("Foo is {0} and bar is {1}.", options.Foo, options.Bar); } So how does this work? Well, it really is very simple. And not. Let’s say it’s not a lot of code, but if you’re like me you might need an Advil after that. First, I defined the signature of the CallStream method as follows: public delegate CallStream CallStream (Action<object> action, object options = null); The delegate define a call stream as something that takes an action (a function of the options) and an optional options object and that returns a delegate of its own type. Tricky, but that actually works, a delegate can return its own type. Then I wrote an implementation of that delegate that calls the action and returns itself: public static CallStream CallStream (Action<object> action, object options = null) { action(options); return CallStream; } Pretty nice, eh? Well, yes and no. What we are doing here is to execute a sequence of actions using an interesting novel syntax. But for this to be actually useful, you’d need to build a more specialized call stream factory that comes with some sort of context (like Dusan did in JavaScript). For example, you could write the following alternate delegate signature that takes a string and returns itself: public delegate StringCallStream StringCallStream(string message); And then write the following call stream (notice the currying): public static StringCallStream CreateDumpCallStream(string dumpPath) { StringCallStream str = null; var dump = File.AppendText(dumpPath); dump.AutoFlush = true; str = s => { dump.WriteLine(s); return str; }; return str; } (I know, I’m not closing that stream; sure; bad, bad Bertrand) Finally, here’s how you use it: CallStreamFactory.CreateDumpCallStream(@".\dump.txt") ("Wow, this really works.") (DateTime.Now.ToLongTimeString()) ("And that is all."); Next step would be to combine this contextual implementation with the one that takes an action parameter and do some really fun stuff. I’m only scratching the surface here. This pattern could reveal itself to be nothing more than a gratuitous mind-bender or there could be applications that we hardly suspect at this point. In any case, it’s a fun new construct. Or is this nothing new? You tell me… Comments are open :)

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  • print a linear linked list into a table

    - by user1796970
    I am attempting to print some values i have stored into a LLL into a readable table. The data i have stored is the following : DEBBIE STARR F 3 W 1000.00 JOAN JACOBUS F 9 W 925.00 DAVID RENN M 3 H 4.75 ALBERT CAHANA M 3 H 18.75 DOUGLAS SHEER M 5 W 250.00 SHARI BUCHMAN F 9 W 325.00 SARA JONES F 1 H 7.50 RICKY MOFSEN M 6 H 12.50 JEAN BRENNAN F 6 H 5.40 JAMIE MICHAELS F 8 W 150.00 i have stored each firstname, lastname, gender, tenure, payrate, and salary into their own List. And would like to be able to print them out in the same format that they are viewed on the text file i read them in from. i have messed around with a few methods that allow me to traverse and print the Lists, but i end up with ugly output. . . here is my code for the storage of the text file and the format i would like to print out: public class Payroll { private LineWriter lw; private ObjectList output; ListNode input; private ObjectList firstname, lastname, gender, tenure, rate, salary; public Payroll(LineWriter lw) { this.lw = lw; this.firstname = new ObjectList(); this.lastname = new ObjectList(); this.gender = new ObjectList(); this.tenure = new ObjectList(); this.rate = new ObjectList(); this.salary = new ObjectList(); this.output = new ObjectList(); this.input = new ListNode(); } public void readfile() { File file = new File("payfile.txt"); try{ Scanner scanner = new Scanner(file); while(scanner.hasNextLine()) { String line = scanner.nextLine(); Scanner lineScanner = new Scanner(line); lineScanner.useDelimiter("\\s+"); while(lineScanner.hasNext()) { firstname.insert1(lineScanner.next()); lastname.insert1(lineScanner.next()); gender.insert1(lineScanner.next()); tenure.insert1(lineScanner.next()); rate.insert1(lineScanner.next()); salary.insert1(lineScanner.next()); } } }catch(FileNotFoundException e) {e.printStackTrace();} } public void printer(LineWriter lw) { String msg = " FirstName " + " LastName " + " Gender " + " Tenure " + " Pay Rate " + " Salary "; output.insert1(msg); System.out.println(output.getFirst()); System.out.println(" " + firstname.getFirst() + " " + lastname.getFirst() + "\t" + gender.getFirst() + "\t" + tenure.getFirst() + "\t" + rate.getFirst() + "\t" + salary.getFirst()); } }

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  • Why is my javascript function sometimes "not defined"?

    - by harpo
    Problem: I call my javascript function, and sometimes I get the error 'myFunction is not defined'. But it is defined. For example. I'll occasionally get 'copyArray is not defined' even in this example: function copyArray( pa ) { var la = []; for (var i=0; i < pa.length; i++) la.push( pa[i] ); return la; } Function.prototype.bind = function( po ) { var __method = this; var __args = []; // sometimes errors -- in practice I inline the function as a workaround __args = copyArray( arguments ); return function() { /* bind logic omitted for brevity */ } } As you can see, copyArray is defined right there, so this can't be about the order in which script files load. I've been getting this in situations that are harder to work around, where the calling function is located in another file that should be loaded after the called function. But this was the simplest case I could present, and appears to be the same problem. It doesn't happen 100% of the time, so I do suspect some kind of load-timing-related problem. But I have no idea what. @Hojou: That's part of the problem. The function in which I'm now getting this error is itself my addLoadEvent, which is basically a standard version of the common library function. @James: I understand that, and there is no syntax error in the function. When that is the case, the syntax error is reported as well. In this case, I am getting only the 'not defined' error. @David: The script in this case resides in an external file that is referenced using the normal <script src="file.js"></script> method in the page's head section. @Douglas: Interesting idea, but if this were the case, how could we ever call a user-defined function with confidence? In any event, I tried this and it didn't work. @sk: This technique has been tested across browsers and is basically copied from the prototype library.

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