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  • How important is graceful degradation of JavaScript? [closed]

    - by Stephen
    Should web developers continue to spend effort progressively enhancing our web applications with JavaScript, ensuring that features gracefully degrade, thereby ensuring accessibility? Or should we spend that time focused on new features or other areas of development? The subtext of that question would be: How many of our customers/clients/users utilize our websites or applications with JavaScript disabled? Do you have any projects with requirements that specifically demand JavaScript functionality (almost all of mine do), and do those requirements also demand graceful degradation? For the sake of asking this question, I pulled up programmers.stackexchange.com without JavaScript enabled, and I was greeted with this message: "Programmers - Stack Exchange works best with JavaScript enabled". It was difficult to log in, albeit the site seemed to generally work okay. (I wasn't able to vote up any questions.) I think this is a satisfactory approach to development. Imagine the effort involved in making all of the site's features work with plain old HTML and server-side logic. On the other hand, I wonder how many users have been alienated by this approach. We've all been trained (at least the good developers among us) to use progressive enhancement and to ensure our web applications' dynamic features degrade gracefully. Is this progressive enhancement just pissing into the wind, or do some of our customers actually utilize certain web services without JavaScript enabled?

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  • Javascript: Machine Constants Applicable?

    - by DavidB2013
    I write numerical routines for students of science and engineering (although they are freely available for use by anybody else as well) and am wondering how to properly use machine constants in a JavaScript program, or if they are even applicable. For example, say I am writing a program in C++ that numerically computes the roots of the following equation: exp(-0.7x) + sin(3x) - 1.2x + 0.3546 = 0 A root-finding routine should be able to compute roots to within the machine epsilon. In C++, this value is specified by the language: DBL_EPSILON. C++ also specifies the smallest and largest values that can be held by a float or double variable. However, how does this convert to JavaScript? Since a Javascript program runs in a web browser, and I don't know what kind of computer will run the program, and JavaScript does not have corresponding predefined values for these quantities, how can I implement my own version of these constants so that my programs compute results to as much accuracy as allowed on the computer running the web browser? My first draft is to simply copy over the literal constants from C++: FLT_MIN: 1.17549435082229e-038 FLT_MAX: 3.40282346638529e+038 DBL_EPSILON: 2.2204460492503131e-16 I am also willing to write small code blocks that could compute these values for each machine on which the program is run. That way, a supercomputer might compute results to a higher accuracy than an old, low-level, PC. BUT, I don't know if such a routine would actually reach the computer, in which case, I would be wasting my time. Anybody here know how to compute and use (in Javascript) values that correspond to machine constants in a compiled language? Is it worth my time to write small programs in Javascript that compute DBL_EPSILON, FLT_MIN, FLT_MIN, etc. for use in numerical routines? Or am I better off simply assigning literal constants that come straight from C++ on a standard Windows PC?

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  • A few questions about how JavaScript works

    - by KayoticSully
    I originally posted on Stack Overflow and was told I might get some better answers here. I have been looking deeply into JavaScript lately to fully understand the language and have a few nagging questions that I can not seem to find answers to (Specifically dealing with Object Oriented programming. I know JavaScript is meant to be used in an OOP manner I just want to understand it for the sake of completeness). Assuming the following code: function TestObject() { this.fA = function() { // do stuff } this.fB = testB; function testB() { // do stuff } } TestObject.prototype = { fC : function { // do stuff } } What is the difference between functions fA and fB? Do they behave exactly the same in scope and potential ability? Is it just convention or is one way technically better or proper? If there is only ever going to be one instance of an object at any given time, would adding a function to the prototype such as fC even be worthwhile? Is there any benefit to doing so? Is the prototype only really useful when dealing with many instances of an object or inheritance? And what is technically the "proper" way to add methods to the prototype the way I have above or calling TestObject.prototype.functionName = function(){} every time? I am looking to keep my JavaScript code as clean and readable as possible but am also very interested in what the proper conventions for Objects are in the language. I come from a Java and PHP background and am trying to not make any assumptions about how JavaScript works since I know it is very different being prototype based. Also are there any definitive JavaScript style guides or documentation about how JavaScript operates at a low level? Thanks!

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  • How to send java.util.logging to log4j?

    - by matt b
    I have an existing application which does all of its logging against log4j. We use a number of other libraries that either also use log4j, or log against Commons Logging, which ends up using log4j under the covers in our environment. One of our dependencies even logs against slf4j, which also works fine since it eventually delegates to log4j as well. Now, I'd like to add ehcache to this application for some caching needs. Previous versions of ehcache used commons-logging, which would have worked perfectly in this scenario, but as of version 1.6-beta1 they have removed the dependency on commons-logging and replaced it with java.util.logging instead. Not really being familiar with the built-in JDK logging available with java.util.logging, is there an easy way to have any log messages sent to JUL logged against log4j, so I can use my existing configuration and set up for any logging coming from ehcache? Looking at the javadocs for JUL, it looks like I could set up a bunch of environment variables to change which LogManager implementation is used, and perhaps use that to wrap log4j Loggers in the JUL Logger class. Is this the correct approach? Kind of ironic that a library's use of built-in JDK logging would cause such a headache when (most of) the rest of the world is using 3rd party libraries instead.

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  • Listening and firing events with Javascript and maybe jQuery

    - by at
    In my Javascript and Flex applications, users often perform actions that I want other Javascript code on the page to listen for. For example, if someone adds a friend. I want my Javascript app to then call something like triggerEvent("addedFriend", name);. Then any other code that was listening for the "addedFriend" event will get called along with the name. Is there a built-in Javascript mechanism for handling events? I'm ok with using jQuery for this too and I know jQuery makes extensive use of events. But with jQuery, it seems that its event mechanism is all based around elements. As I understand, you have to tie a custom event to an element. I guess I can do that to a dummy element, but my need has nothing to do with DOM elements on a webpage. Should I just implement this event mechanism myself?

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  • Executing Javascript without a browser?

    - by Daniel
    I am looking into Javascript programming without a browser. I want to run scripts from the Linux or Mac OS X command line, much like we run any other scripting language (ruby, php, perl, python...) $ javascript my_javascript_code.js I looked into spider monkey (Mozilla) and v8 (Google), but both of these appear to be embedded. Is anyone using Javascript as a scripting language to be executed from the command line? If anyone is curious why I am looking into this, I've been poking around node.js

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  • Should I be using a JavaScript SPA designed when security is important

    - by ryanzec
    I asked something kind of similar on stackoverflow with a particular piece of code however I want to try to ask this in a broader sense. So I have this web application that I have started to write in backbone using a Single Page Architecture (SPA) however I am starting to second guess myself because of security. Now we are not storing and sending credit card information or anything like that through this web application but we are storing sensitive information that people are uploading to us and will have the ability to re-download too. The obviously security concern that I have with JavaScript is that you can't trust anything that comes from JavaScript however in a Backbone SPA application, everything is being sent through JavaScript. There are two security features that I will have to build in JavaScript; permissions and authentication. The authentication piece is just me override the Backbone.Router.prototype.navigate method to check the fragment it is trying to load and if the JavaScript application.session.loggedIn is not set to true (and they are not viewing a none authenticated page), they are redirected to the login page automatically. The user could easily modify application.session.loggedIn to equal true (or modify Backbone.Router.prototype.navigate method) but then they would also have to not so easily dynamically embedded a link into the page (or modify a current one) that has the proper classes, data-* attributes, and href values to then load a page that should only be loaded when they user has logged in (and has the permissions). So I have an acl object that deals with the permissions stuff. All someone would have to do to view pages or parts of pages they should not be able to is to call acl.addPermission(resource, permission) with the proper permissions or modify the acl.hasPermission() to always return true and then navigate away and then back to the page. Now certain things is EMCAScript 5 like Object.seal() or Object.freeze() would help with some of this however we have to support IE 8 which does not support those pieces of functionality. Now the REST API also performs security checks on every request so technically even if they are able to see parts of the interface that they should not be able to, they still should not be able to actually affect any data. The main benefits for me in developing a JavaScript SPA application is that the application is a lot more responsive since it is only transferring the minimum amount of JSON data for the requested action and performing the minimum amount of work too. There are also other things that I think are beneficial like you are going to have to develop an API for the data (which is good if you want expand your application to different platforms/technologies) or their is more of a separation between front-end and back-end however if security is a concern, it is really wise to go down the road of a JavaScript SPA application for the front-end?

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  • Logging hurts MySQL performance - but, why?

    - by jimbo
    I'm quite surprised that I can't see an answer to this anywhere on the site already, nor in the MySQL documentation (section 5.2 seems to have logging otherwise well covered!) If I enable binlogs, I see a small performance hit (subjectively), which is to be expected with a little extra IO -- but when I enable a general query log, I see an enormous performance hit (double the time to run queries, or worse), way in excess of what I see with binlogs. Of course I'm now logging every SELECT as well as every UPDATE/INSERT, but, other daemons record their every request (Apache, Exim) without grinding to a halt. Am I just seeing the effects of being close to a performance "tipping point" when it comes to IO, or is there something fundamentally difficult about logging queries that causes this to happen? I'd love to be able to log all queries to make development easier, but I can't justify the kind of hardware it feels like we'd need to get performance back up with general query logging on. I do, of course, log slow queries, and there's negligible improvement in general usage if I disable this. (All of this is on Ubuntu 10.04 LTS, MySQLd 5.1.49, but research suggests this is a fairly universal issue)

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  • IIS 7.5 FTP Service crashes after installation of Advanced Logging 1.0 Module

    - by Jeremy
    I've recently been tasked with setting up two new productions servers for an ASP.Net application. The servers sit behind a F5 Load Balancer, which in turn forwards the end users IP address forward via the standard X_Forwarded_For HTTP Header. All of the reading that I have done suggests that I need to install the IIS Advanced Logging Module in order to take advantage of the X_Forwarded_For HTTP Header. Some quick background: Both of the web servers are Windows 2008 R2 Standard (x64), with IIS 7.5 installed and configured. The FTP Role has also been installed, configured and is operational. The Issue After installing the IIS Advanced Logging module via the Web Platform Installer, I noticed the following Error in the Event Viewer: The FTP Service encountered an error trying to read configuration data from file \?\C:\Windows\system32\inetsrv\config\applicationHost.config, line number 374. The error message is: Unrecognized element 'advancedLogging' Trying to connect over FTP to either of the web servers results in a 530. I've spent 2 hours scouring Google trying to find a solution, short of uninstalling the Advanced Logging Module. As far as I can tell, there is no way to turn off Advanced Logging on a site per site basis. Help would be appreciated.

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  • How can I disable logging in Tomcat 7?

    - by WilliamMayor
    I have a Tomcat 7 server running in a VM that has very little disk space (20G). Over the course of a few days Tomcat will fill the space with logging info (usually about 15G before it runs out). I've tried turning down the log level (from INFO to SEVERE) in the logging.properties file, I've also tried sending the log info to /dev/null. It doesn't seem to work as I still get a full log directory after no time at all. Can I put a file size limit on the log files? Is something overriding the properties I'm setting? Where can I find this information? My Google Fu just returns information about logging from within an application using JULI.

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  • lighttpd silently stops logging

    - by Max Cantor
    I'm on a Slicehost 256MB VPS with Ubuntu 9.04 (Jaunty). lighttpd is the only web server process running; it listens on port 80. My lighttpd.conf can be found here. I'm using Ubuntu's default logrotate setup for lighty. At seemingly random times, lighttpd will stop logging. It is not correlated with log rotation--that is, the errors do not occur when logrotate kicks in. What happens is, I will verify that the server is serving files by hitting a URL with my browser, and I will verify that it is not logging by checking access.log and seeing that the GET request I just made is not there. Using init.d to restart the process starts logging again, without truncating or rotating the log file. That is, new requests will be logged at the end of the existing access.log file. There are no cron jobs running on this box. Any ideas?

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  • Javascript in XSL that is loaded by Javascript

    - by James Armstead
    Is there anyway to have javascript run when a XSL sheet has been applied to an XML file by Javascript? I am using a JQuery plugin to apply the sheet to the xml but the javascript that is located inside of the XSL file will not run. I put the Javascript at the bottom of the file and it still does not run.. I can't seem to get an alert to even run?

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  • using javascript onchange to fill a calendar

    - by scatman
    i have a calendar and a textbox in my c# asp.net application. when a user enters a date in the textbox, the selected date in the calendar should become the date entered in the text box. the hard part is that i need to do this in javascript. what i have now is this: <asp:TextBox ID="txtDate" runat="server" onchange="javascript: Changed( this );" /> <asp:Calendar ID="calDate" runat="server" /> <script type="text/javascript"> var calendarID = ''; function Changed(textControl) { var date = Date.parse(textControl.value); //this is giving me the date in seconds var cal = document.getElementById(calendarID); } </script> and i am setting calendarID in this way: <script type="text/javascript"> calendarID = "<%=calDate.ClientID%>"; </script> there is no cal.selectedDate or anything like this... any help?

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  • simple and reliable centralized logging inside Amazon VPC

    - by Nakedible
    I need to set up centralized logging for a set of servers (10-20) in an Amazon VPC. The logging should be as to not lose any log messages in case any single server goes offline - or in the case that an entire availability zone goes offline. It should also tolerate packet loss and other normal network conditions without losing or duplicating messages. It should store the messages durably, at the minimum on two different EBS volumes in two availability zones, but S3 is a good place as well. It should also be realtime so that the messages arrive within seconds of their generation to two different availability zones. I also need to sync logfiles not generated via syslog, so a syslog-only centralized logging solution would not fulfill all the needs, although I guess that limitation could be worked around. I have already reviewed a few solutions, and I will list them here: Flume to Flume to S3: I could set up two logservers as Flume hosts which would store log messages either locally or in S3, and configure all the servers with Flume to send all messages to both servers, using the end-to-end reliability options. That way the loss of a single server shouldn't cause lost messages and all messages would arrive in two availability zones in realtime. However, there would need to be some way to join the logs of the two servers, deduplicating all the messages delivered to both. This could be done by adding a unique id on the sending side to each message and then write some manual deduplication runs on the logfiles. I haven't found an easy solution to the duplication problem. Logstash to Logstash to ElasticSearch: I could install Logstash on the servers and have them deliver to a central server via AMQP, with the durability options turned on. However, for this to work I would need to use some of the clustering capable AMQP implementations, or fan out the deliver just as in the Flume case. AMQP seems to be a yet another moving part with several implementations and no real guidance on what works best this sort of setup. And I'm not entirely convinced that I could get actual end-to-end durability from logstash to elasticsearch, assuming crashing servers in between. The fan-out solutions run in to the deduplication problem again. The best solution that would seem to handle all the cases, would be Beetle, which seems to provide high availability and deduplication via a redis store. However, I haven't seen any guidance on how to set this up with Logstash and Redis is one more moving part again for something that shouldn't be terribly difficult. Logstash to ElasticSearch: I could run Logstash on all the servers, have all the filtering and processing rules in the servers themselves and just have them log directly to a removet ElasticSearch server. I think this should bring me reliable logging and I can use the ElasticSearch clustering features to share the database transparently. However, I am not sure if the setup actually survives Logstash restarts and intermittent network problems without duplicating messages in a failover case or similar. But this approach sounds pretty promising. rsync: I could just rsync all the relevant log files to two different servers. The reliability aspect should be perfect here, as the files should be identical to the source files after a sync is done. However, doing an rsync several times per second doesn't sound fun. Also, I need the logs to be untamperable after they have been sent, so the rsyncs would need to be in append-only mode. And log rotations mess things up unless I'm careful. rsyslog with RELP: I could set up rsyslog to send messages to two remote hosts via RELP and have a local queue to store the messages. There is the deduplication problem again, and RELP itself might also duplicate some messages. However, this would only handle the things that log via syslog. None of these solutions seem terribly good, and they have many unknowns still, so I am asking for more information here from people who have set up centralized reliable logging as to what are the best tools to achieve that goal.

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  • Javascript clears a variable after there is no further reference it

    - by Praveen Prasad
    It is said, javascript clears a variable from memory after its being referenced last. just for the sake of this question i created a JS file with only one variable; //file start //variable defined var a=["Hello"] //refenence to that variable alert(a[0]); // //file end no further reference to that variable, so i expect javascript to clear varaible 'a' Now i just ran this page and then opened firebug and ran this code alert(a[0]); Now this alerts the value of variable, If the statement "Javascript clears a variable after there is no further reference it" is true how come alert() shows its value. Is it because all variable defined in global context become properties of window object, and since even after the execution file window objects exist so does it properties.

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  • Why does Java Logging API create so many files?

    - by rgksugan
    I am using java logging api to log errors in my exception. I am writing these errors to a log file. When i run my program i find a lot of files created.There are around 50 files created. Is there any mistake in my code or is it normal? Here goes the code try { logger = Logger.getLogger(Reciever.class.getName()); fileHandler = new FileHandler("Applicationlog.log", true); logger.addHandler(fileHandler); logger.setLevel(Level.ALL); SimpleFormatter formatter = new SimpleFormatter(); fileHandler.setFormatter(formatter); } catch (IOException ex) { logger.log(Level.SEVERE, null, ex); } catch (SecurityException ex) { logger.log(Level.SEVERE, null, ex); }

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  • JavaScript Data Binding Frameworks

    - by dwahlin
    Data binding is where it’s at now days when it comes to building client-centric Web applications. Developers experienced with desktop frameworks like WPF or web frameworks like ASP.NET, Silverlight, or others are used to being able to take model objects containing data and bind them to UI controls quickly and easily. When moving to client-side Web development the data binding story hasn’t been great since neither HTML nor JavaScript natively support data binding. This means that you have to write code to place data in a control and write code to extract it. Although it’s certainly feasible to do it from scratch (many of us have done it this way for years), it’s definitely tedious and not exactly the best solution when it comes to maintenance and re-use. Over the last few years several different script libraries have been released to simply the process of binding data to HTML controls. In fact, the subject of data binding is becoming so popular that it seems like a new script library is being released nearly every week. Many of the libraries provide MVC/MVVM pattern support in client-side JavaScript apps and some even integrate directly with server frameworks like Node.js. Here’s a quick list of a few of the available libraries that support data binding (if you like any others please add a comment and I’ll try to keep the list updated): AngularJS MVC framework for data binding (although closely follows the MVVM pattern). Backbone.js MVC framework with support for models, key/value binding, custom events, and more. Derby Provides a real-time environment that runs in the browser an in Node.js. The library supports data binding and templates. Ember Provides support for templates that automatically update as data changes. JsViews Data binding framework that provides “interactive data-driven views built on top of JsRender templates”. jQXB Expression Binder Lightweight jQuery plugin that supports bi-directional data binding support. KnockoutJS MVVM framework with robust support for data binding. For an excellent look at using KnockoutJS check out John Papa’s course on Pluralsight. Meteor End to end framework that uses Node.js on the server and provides support for data binding on  the client. Simpli5 JavaScript framework that provides support for two-way data binding. WinRT with HTML5/JavaScript If you’re building Windows 8 applications using HTML5 and JavaScript there’s built-in support for data binding in the WinJS library.   I won’t have time to write about each of these frameworks, but in the next post I’m going to talk about my (current) favorite when it comes to client-side JavaScript data binding libraries which is AngularJS. AngularJS provides an extremely clean way – in my opinion - to extend HTML syntax to support data binding while keeping model objects (the objects that hold the data) free from custom framework method calls or other weirdness. While I’m writing up the next post, feel free to visit the AngularJS developer guide if you’d like additional details about the API and want to get started using it.

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  • What should JavaScript be renamed to [closed]

    - by Evan Plaice
    Background: I have been watching Douglas Crockford's series of presentation about JavaScript History (which I highly recommend) lately and a one comment of his specifically piqued my attention. The trademark for 'JavaScript' is owned by Oracle History: Due to time constraints at Netscape, the language was literally written in weeks and released in very buggy form. To make it seem more appealing, Netscape picked JavaScript to appeal to the massively growing population of Java developers. Unfortunately, this pissed off Sun and stirred up a lot of controversy between the two organizations. At some point, they came to an agreement whereby Netscape was given permission to use the name as long as Sun owned the trademark. Some people incorrectly refer to JavaScript as ECMAScript because that's where the standard for the language is registered but, aside from it's current marketing-driven label, it doesn't really have a name. Fast Forward Sun goes down only to be swallowed by Oracle, who has no reservations about litigating for profit, now owns the name. So... If Oracle decides and forces JavaScript to take on a new name, what name would best represent the language?

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  • Performance: recursion vs. iteration in Javascript

    - by mastazi
    I have read recently some articles (e.g. http://dailyjs.com/2012/09/14/functional-programming/) about the functional aspects of Javascript and the relationship between Scheme and Javascript (the latter was influenced by the first, which is a functional language, while the O-O aspects are inherited from Self which is a prototyping-based language). However my question is more specific: I was wondering if there are metrics about the performance of recursion vs. iteration in Javascript. I know that in some languages (where by design iteration performs better) the difference is minimal because the interpreter / compiler converts recursion into iteration, however I guess that probably this is not the case of Javascript since it is, at least partially, a functional language.

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  • How to use html and JavaScript in Content Editor web part in SharePoint2010

    - by ybbest
    Here are the steps you need to take to use html and JavaScript in content editor web part. 1. Edit a site page and add a content editor web part on the page. 2. After the content editor is added to the page, it will display on the page like shown below 3. Next, upload your html and JavaScript content as a text file to a document library inside your SharePoint site. Here is the content in the document <script type="text/javascript"> alert("Hello World"); </script> 4. Edit the content editor web part and reference the file you just uploaded. 5. Save the page and you will see the hello world prompt. References: http://stackoverflow.com/questions/5020573/sharepoint-2010-content-editor-web-part-duplicating-entries http://sharepointadam.com/2010/08/31/insert-javascript-into-a-content-editor-web-part-cewp/

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  • data handling with javascript

    - by Vincent Warmerdam
    Python has a very neat package called pandas which allows for quick data transformation; tables, aggregation, that sort of thing. A lot of these types of functionality can also be found in the python itertools module. The plyR package in R is also very similar. Usually one woud use this functionality to produce a table which is later visualized with a plot. I am personally very fond of d3, and I would like to allow the user to first indicate what type of data aggregation he wants on the dataset before it is visualized. The visualisation in question involves making a heatmap where the user gets to select the size of the bins of the heatmap beforehand (I want d3 to project this through leaflet). I want to visually select the ideal size of the bins for the heatmap. The way I work now is that I take the dataset, aggregate it with python and then manually load it in d3. This is a process that takes a lot of human effort and I was wondering if the data aggregation can be done through the javascript of the browser. I couldn't find a package for javascript specifically built for data, suggesting (to me) that this is a bad idea and that one should not use javascript for the data handling. Is there a good module/package for javascript to handle data aggregation? Is it a good/bad idea to do the data aggregation in javascript (performance wise)?

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  • JavaScript evolution -- weeding out the confusion [closed]

    - by good_computer
    There was JavaScript v1.3 (I guess) that we all started with. Then there was JavaScript 2.0 that Adobe implemented (ActionScript) but was abandoned later. Then came E4X. Then ES5. There is also ES harmony. I am really confused about which version is the latest and where is the standards body going. Can someone describe the whole chronology of JavaScript / ECMAScript evolution and the important differences between those versions?

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