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• JavaScript: scroll position (Webkit engine) [migrated]

  - by Julien

  I'm currently trying to use JavaScript to find out how far down the page the user has scrolled; for Firefox 8.0, the keyword is pageYOffset. To say things mechanically: The page has a certain height. In Firefox, the useful object is document.documentElement.scrollHeight. The browser's visible area also has a certain height. In Firefox, the object is window.innerHeight; in IE8, document.documentElement.clientHeight. I need to know where the user is in the page vertically; in other words, how many pixels down the page the user has scrolled. Does Webkit have a DOM object that refers to the current scroll position? Thank you.

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• Experience embedding javascript

  - by deft_code

  I'm looking into scripting languages to embed in my game. I've always assumed Lua was the best choice, but I've read some recent news about embedding V8 as was considering using it instead. My question is two fold: Does anyone with experience embedding v8 (or another javascript engine) recommend it? How does it compare with embedding Lua? I like that v8 has a c++ embedding API. However Lua API has had lots of time to be refined (newer isn't always better and all that). Note: At this point I'm not too concerned with which is better language or which library has better performance. I'm only asking about ease of embedding.

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• Comparisons of Javascript 'data grids'?

  - by Joe

  I've found plenty of questions between here and StackExchange of people asking for the 'best' data grid / data table, or one that has a particular feature, and plenty of lists out there (of various ages) listing the various data grid implementations ... but is anyone aware of any matrix of what features the various solutions implement? (eg, allow shift-click to select multiple; support checkboxes for selection; can update a regular table in-place; allow editing of cells; support websql or indexeddb for local caching; which browsers they support; infinite scroll; etc.) There's a generic 'javascript framework' comparison on wikipedia, which would be the sort of thing I'm looking for, but it doesn't go into detail on data grids. (which makes sense, as so many are extensions, not core features of those frameworks, and in the case of jQuery, there's lots of 'em.)

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• Has Dart something useful that javascript doesn't have?

  - by marko

  http://www.dartlang.org/ I've checked out the site very briefly, and got curious. Is there any advantages of using Dart? Is it just a replacement for javascript? It looks like simpler java. Writing quite a lot of C# at work, the language feels very much like what I'm used to, so learning the syntax looks like a breeze to learn. Has anybody any opinions or experiences with the language? (Compared to coffeescript (= I'm not doing ruby syntax) the syntax looks more familiar to me).

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• in javascript whay use " var that = this "

  - by tarek11011

  hi i am new with javascript What is the benefit of using this line var that = this An example function Person( firstname, lastname, age ) { this.firstname = firstname; this.lastname = lastname; this.age = age; getfullname = function() { return firstname + “ “ + lastname; }; var that = this; this.sayHi = function() { document.write( “Hi my name is “ + getfullname() + “ and I am “ + that.age + “years old.”); }; } thanks

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• in javascript why use " var that = this "

  - by tarek11011

  hi i am new with javascript What is the benefit of using this line var that = this An example function Person( firstname, lastname, age ) { this.firstname = firstname; this.lastname = lastname; this.age = age; getfullname = function() { return firstname + “ “ + lastname; }; var that = this; this.sayHi = function() { document.write( “Hi my name is “ + getfullname() + “ and I am “ + that.age + “years old.”); }; } thanks

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• php variable scope in oop

  - by mr o

  Hi, I wonder if anyone can help out here, I'm trying to understand how use an objects properties across multiple non class pages,but I can't seem to be able to get my head around everything i have tried so far. For example a class called person; class person { static $name; } but i have a number of different regular pages that want to utilize $name across the board. I have trying things like this; pageone.php include "person.php"; $names = new Person(); echo person::$name; names::$name='bob'; pagetwo.php include "person.php"; echo person::$name; I can work with classes to the extent I'm OK as long as I am creating new instances every page, but how can make the properties of one object available to all, like a shared variable ? Thanks

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• Licensing a JavaScript library

  - by Kendall Frey

  I am developing a free, open-source (duh) JavaScript library, and wondering how to license it. I was considering the GNU GPL, but I heard that I must distribute the license with the software, and I'm not sure anymore. I would like the library to be available much like jQuery: In a free, downloadable script, preferably in either original or minified form. Am I mistaken about the GNU GPL license terms? jQuery is dual licensed under GNU GPL or MIT licenses. How does the GPL apply to single script files like that? Can I license my library with nothing more than a few sentences in the script file? Is there another license that better suits my needs? What would be nice is a license that allows you to put the URL in the source, for people to read if they want. I don't know that many do, unless I am mistaken. I am generally looking to release the library as free software like the GPL specifies, but don't want to have to force licensees to download the full license unless they wish to read it.

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• Need advice on OOP philosophy

  - by David Jenings

  I'm trying to get the wheels turning on a large project in C#. My previous experience is in Delphi, where by default every form was created at applicaton startup and form references where held in (gasp) global variables. So I'm trying to adapt my thinking to a 100% object oriented environment, and my head is spinning just a little. My app will have a large collection of classes Most of these classes will only really need one instance. So I was thinking: static classes. I'm not really sure why, but much of what I've read here says that if my class is going to hold a state, which I take to mean any property values at all, I should use a singleton structure instead. Okay. But there are people out there who for reasons that escape me, think that singletons are evil too. None of these classes is in danger of being used anywhere except in this program. So they could certainly work fine as regular objects (vs singletons or static classes) Then there's the issue of interaction between objects. I'm tempted to create a Global class full of public static properties referencing the single instances of many of these classes. I've also considered just making them properties (static or instance, not sure which) of the MainForm. Then I'd have each of my classes be aware of the MainForm as Owner. Then the various objects could refer to each other as Owner.Object1, Owner.Object2, etc. I fear I'm running out of electronic ink, or at least taxing the patience of anyone kind enough to have stuck with me this long. I hope I have clearly explained my state of utter confusion. I'm just looking for some advice on best practices in my situation. All input is welcome and appreciated. Thanks in advance, David Jennings

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• Will Google treat this JavaScript code as a bad practice?

  - by Mathew Foscarini

  I have a website that provides a custom UX experience implemented via JavaScript. When JavaScript is disabled in the browser the website falls back to CSS for the layout. To make this possible I've added a noJS class to the <body> and quickly remove it via JavaScript. <body class="noJS layout-wide"> <script type="text/javascript">var b=document.getElementById("body");b.className=b.className.replace("noJS","");</script> This caused a problem when the page loads and JavaScript is enabled. The body immediately has it's noJS class removed, and this causes the layout to appear messed up until the JavaScript code for layout is executed (at bottom of the page). To solve this I hide each article via JavaScript by adding a CSS class fix which is display:none as each article is loaded. <article id="q-3217">....</article> <script type="text/javascript">var b=document.getElementById("q-3217");b.className=b.className+" fix";</script> After the page is ready I show all the articles in the correct layout. I've read many times in Google's documentation not to hide content. So I'm worried that the Google will penalize my website for doing this.

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• javascript fixed timestep gameloop with requestanimation frame

  - by coffeecup

  hello i just started to read through several articles, including http://gafferongames.com/game-physics/fix-your-timestep/ ...://gamedev.stackexchange.com/questions/1589/fixed-time-step-vs-variable-time-step/ ...//dewitters.koonsolo.com/gameloop.html ...://nokarma.org/2011/02/02/javascript-game-development-the-game-loop/index.html my understanding of this is that i need the currentTime and the timeStep size and integrate all states to the next state the time which is left is then passed into the render function to do interpolation i tried to implement glenn fiedlers "the final touch", whats troubling me is that each FrameTime is about 15 (ms) and the update loop runs at about 1500 fps which seems a little bit off? heres my code this.t = 0 this.dt = 0.01 this.currTime = new Date().getTime() this.accumulator = 0.0 this.animate() animate: function(){ var newTime = new Date().getTime() , frameTime = newTime - this.currTime , alpha if ( frameTime > 0.25 ) frameTime = 0.25 this.currTime = newTime this.accumulator += frameTime while (this.accumulator >= this.dt ) { this.prev_state = this.curr_state this.update(this.t,this.dt) this.t += this.dt this.accumulator -= this.dt } alpha = this.accumulator / this.dt this.render( this.t, this.dt, alpha) requestAnimationFrame( this.animate ) } also i would like to know, are there differences between glenn fiedlers implementation and the last solution presented here ? gameloop1 gameloop2 [ sorry couldnt post more than 2 links.. ] edit : i looked into it again and adjusted the values this.currTime = new Date().getTime() this.accumulator = 0 this.p_t = 0 this.p_step = 1000/100 this.animate() animate: function(){ var newTime = new Date().getTime() , frameTime = newTime - this.currTime , alpha if(frameTime > 25) frameTime = 25 this.currTime = newTime this.accumulator += frameTime while(this.accumulator >= this.p_step){ // prevstate = currState this.update() this.p_t+=this.p_step this.accumulator -= this.p_step } alpha = this.accumulator / this.p_step this.render(alpha) requestAnimationFrame( this.animate ) now i can set the physics update rate, render runs at 60 fps and physics update at 100 fps, maybe someone could confirm this because its the first time i'm playing around with game development :-)

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• Semi Fixed-timestep ported to javascript

  - by abernier

  In Gaffer's "Fix Your Timestep!" article, the author explains how to free your physics' loop from the paint one. Here is the final code, written in C: double t = 0.0; const double dt = 0.01; double currentTime = hires_time_in_seconds(); double accumulator = 0.0; State previous; State current; while ( !quit ) { double newTime = time(); double frameTime = newTime - currentTime; if ( frameTime > 0.25 ) frameTime = 0.25; // note: max frame time to avoid spiral of death currentTime = newTime; accumulator += frameTime; while ( accumulator >= dt ) { previousState = currentState; integrate( currentState, t, dt ); t += dt; accumulator -= dt; } const double alpha = accumulator / dt; State state = currentState*alpha + previousState * ( 1.0 - alpha ); render( state ); } I'm trying to implement this in JavaScript but I'm quite confused about the second while loop... Here is what I have for now (simplified): ... (function animLoop(){ ... while (accumulator >= dt) { // While? In a requestAnimation loop? Maybe if? ... } ... // render requestAnimationFrame(animLoop); // stand for the 1st while loop [OK] }()) As you can see, I'm not sure about the while loop inside the requestAnimation one... I thought replacing it with a if but I'm not sure it will be equivalent... Maybe some can help me.

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• Lightweight, dynamic, fully JavaScript web UI library recommendations

  - by Matt Greer

  I am looking for recommendations for a lightweight, dynamic, fully JavaScript UI library for websites. Doesn't have to be amazing visually, the end result is for simple demos I create. What I want can be summed up as "Ext-like, but not GPL'ed, and a much smaller footprint". I want to be able to construct UIs dynamically and fully through code. My need for this is currently driven by this particle designer. Depending on what query parameters you give it, the UI components change, example 1, example2. Currently this is written in Ext, but Ext's license and footprint are turn offs for me. I like UKI a lot, but it's not very good for dynamically building UIs since everything is absolutely positioned. Extending Uki to support that is something I am considering. Ideally the library would let me make UIs with a pattern along the lines of: var container = new SomeUI.Container(); container.add(new SomeUI.Label('Color Components')); container.add(new SomeUI.NumberField('R')); container.add(new SomeUI.NumberField('G')); container.add(new SomeUI.NumberField('B')); container.add(new SomeUI.CheckBox('Enable Alpha')); container.renderTo(someDiv);

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• Inheritance Problem in Perl OOP

  - by Sam

  Hello, I have a sub class that calls a method from a super class. and the method in the super class use a method that is defined in the super class as asbstract(not really abstract) but implemented in the sub class. for example: package BaseClass; sub new { } sub method1 { return someAbstractMethod(); } sub someAbtsractMethod { die "oops, this is an abstract method that should be implemented in a subclass" ; } 1; package SubClass; sub new { } sub someAbtsractMethod { print "now we implement the asbtract method"; } 1; now when I do: $sub = new SubClass(); $sub-method1(); It calls the abstract message and i get the specified error message. if I took off the abstractmethod from the super class and just leave the implementation in the subclass, It does not recognize the method and I get subroutine abstractmethod not found error.

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• Isometric Movement in Javascript In the DOM

  - by deep

  I am creating a game using Javascript. I am not using the HTML5 Canvas Element. The game requires both side view controlles, and Isometric controls, hence the movementMode variable. I have got the specific angles, but I am stuck on an aspect of this. https://chillibyte.makes.org/thimble/movement function draw() { if (keyPressed) { if (whichKey == keys.left) { move(-1,0) } if (whichKey == keys.right) { move(1,0) } if (whichKey == keys.up) { move(0,-1) } if (whichKey == keys.down) { move(0,1) } } } This gives normal up, down , left, and right. i want to refactor this so that i can plugin two variables into the move() function, which will give the movement wanted. Now for the trig. /| / | / | y / | /a___| x Take This Right angled Triangle. given that x is 1, y must be equal to tan(a) That Seems right. However, when I do Math.tan(45), i get a number similar to 1.601. Why? To Sum up this question. I have a function, and i need a function which will converts an angle to a value, which will tell me the number of pixels that i need to go up by, if i only go across 1. Is it Math.tan that i want? or is it something else?

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• Is it a oop good design ?

  - by remi bourgarel

  Hi all, I'd like to know what you think about this part of our program is realized : We have in our database a list of campsite. Partners call us to get all the campsites near a GPS location or all the campsites which provide a bar (we call it a service). So how I realized it ? Here is our database : Campsite - ID - NAME - GPS_latitude - GPS_longitude CampsiteServices -Campsite_ID -Services_ID So my code (c# but it's not relevant, let say it's an OO language) looks like this public class SqlCodeCampsiteFilter{ public string SqlCode; public Dictionary<string, object> Parameters; } interface ISQLCampsiteFilter{ SqlCodeEngineCore CreateSQLCode(); } public class GpsLocationFilter : ISQLCampsiteFilter{ public float? GpsLatitude; public float? GpsLongitude; public SqlCodeEngineCore CreateSQLCode() { --return an sql code to filter on the gps location like dbo.getDistance(@gpsLat,@gpsLong,campsite.GPS_latitude,campsite.GPS_longitude) with the parameters } } public class ServiceFilter : : ISQLCampsiteFilter{ public int[] RequiredServicesID; public SqlCodeEngineCore CreateSQLCode() { --return an sql code to filter on the services "where ID IN (select CampsiteServices.Service_ID FROm CampsiteServices WHERE Service_ID in ...) } } So in my webservice code : List<ISQLFilterEngineCore> filters = new List<ISQLFilterEngineCore>(); if(gps_latitude.hasvalue && gps_longitude.hasvalue){ filters.Add (new GpsLocationFilter (gps_latitude.value,gps_longitude.value)); } if(required_services_id != null){ filters.Add (new ServiceFilter (required_services_id )); } string sql = "SELECT ID,NAME FROM campsite where 1=1" foreach(ISQLFilterEngineCore aFilter in filters){ SqlCodeCampsiteFilter code = aFilter.CreateSQLCode(); sql += code.SqlCode; mySqlCommand.AddParameters(code.Parameters);//add all the parameters to the sql command } return mySqlCommand.GetResults(); 1/ I don't use ORM for the simple reason that the system exists since 10 years and the only dev who is here since the beginning is starting to learn about difference between public and private. 2/ I don't like SP because : we can do override, and t-sql is not so funny to use :) So what do you think ? Is it clear ? Do you have any pattern that I should have a look to ? If something is not clear please ask

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• Duplication of code (backend and javascript - knockout)

  - by Michal B.

  We have a new developer in our team. He seems a smart guy (he just came in so I cannot really judge). He started with implementing some small enhancements in the project (MVC3 web application using javascript - jquery and knockout). Let's say we have two values: A - quite complex calculation C - constant B = A + C On the screen there is value B and user can change it (normal texbox). When B changes, A changes as well because C is constant. So there is linear dependency between A and B. Now, all the calculations are done in the backend, but we need to recalculate A as user changes B (in js, I would use knockout). I thought about storing old A and B and when B changes by 10 then we know that new A will be old A + 10. He says this is dirty, because it's duplication of code (we make use of the fact that they are dependent and according to him that should be only in one place in our app). I understand it's not ideal, but making AJAX request after every key press seems a bit too much. It's a really small thing and I would not post if we haven't had long discussion about it. How do you deal with such problems? Also I can imagine that using knockout implies lots of calculations on the client side, which very often leads to duplication of the same calculations from the backend. Does anyone have links to some articles/thoughts on this topic?

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• C# OOP File Structure?

  - by Soo

  Hey SO, I just started programming with objects recently and am trying to learn good habits early on. The way I plan to structure my application is to have two files: 1: Program.cs - This file will contain the main logic for the application 2: Class.cs - This file will contain all of the class definitions Pretty simple. What I'm wondering if I should have any more files for ... well, you tell me. Any help would be appreciated.

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• OOP in PHP: Class-function from a variable?

  - by Martti Laine

  Hello Is it possible to call functions from class like this: $class = new class; $function_name = "do_the_thing"; $req = $class->$function_name(); Something similar solution, this doesn't seem to work? Martti Laine

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• Learning PHP OOP

  - by Ryan Murphy

  I have been coding PHP for about 2 years now and I THINK that I have a very good grasps of the fundamental parts of PHP, i.e. Functions foreach/IF statements sessions/cookies POST/GET Amongst a few others. I want to move on to learning OOP PHP now, so learning how to use classes and making it a really valuable skill. I have 1 requirement, the source must be a respected source that doesn't teach developers bad habits. I have the book: PHP and MySQL Web Development However, as useful as that is I would like an online source. I would like to know from people with experience in OOP PHP, how and where did they learn OOP PHP. Obviously by doing, but I would really appreciate some great resources which help me along the way.

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• New "delay" keyword for JavaScript

  - by Van Coding

  I had a great idea for a new javascript keyword "delay", but I don't know what I can do to bring it to the new specification. Also I want to know what you guys think about it and if it's even realistic. What does the delay keyword ? The delay keyword does nothing more than stop the execution of the current stack and immediately continues to the next "job" in the queue. But that's not all! Instead of discarding the stack, it adds it to the end of the queue. After all "jobs" before it are done, the stack continues to execute. What is it good for? delay could help make blocking code non-blocking while it still looks like synchronous code. A short example: setTimeout(function(){ console.log("two"); },0); console.log("one"); delay; //since there is currently another task in the queue, do this task first before continuing console.log("three"); //Outputs: one, two, three This simple keyword would allow us to create a synchronous-looking code wich is asynchronous behind the scenes. Using node.js modules, for example, would no longer be impossible to use in the browser without trickery. There would be so many possibilites with such a keyword! Is this pattern useful? What can I do to bring this into the new ECMAscript specification? Note: I asked this previously on Stack Overflow, where it was closed.

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• OOP - Handling Automated Instances of a Class - PHP

  - by dscher

  This is a topic that, as a beginner to PHP and programming, sort of perplexes me. I'm building a stockmarket website and want users to add their own stocks. I can clearly see the benefit of having each stock be a class instance with all the methods of a class. What I am stumped on is the best way to give that instance a name when I instantiate it. If I have: class Stock() { ....doing stuff..... } what is the best way to give my instances of it a name. Obviously I can write: $newStock = new Stock(); $newStock.getPrice(); or whatever, but if a user adds a stock via the app, where can the name of that instance come from? I guess that there is little harm in always creating a new child with $newStock = new Stock() and then storing that to the DB which leads me to my next question! What would be the best way to retrieve 20 user stocks(for example) into instances of class Stock()? Do I need to instantiate 20 new instances of class Stock() every time the user logs in or is there something I'm missing? I hope someone answers this and more important hope a bunch of people answer this and it somehow helps someone else who is having a hard time wrapping their head around what probably leads to a really elegant solution. Thanks guys!

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• Authorization in a more purely OOP style...

  - by noblethrasher

  I've never seen this done but I had an idea of doing authorization in a more purely OO way. For each method that requires authorization we associate a delegate. During initialization of the class we wire up the delegates so that they point to the appropriate method (based on the user's rights). For example: class User { private deleteMemberDelegate deleteMember; public StatusMessage DeleteMember(Member member) { if(deleteMember != null) { deleteMember(member); } } //other methods defined similarly... User(string name, string password) //cstor. { //wire up delegates based on user's rights. //Thus we handle authentication and authorization in the same method. } } This way the client code never has to explictly check whether or not a user is in a role, it just calls the method. Of course each method should return a status message so that we know if and why it failed. Thoughts?

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• Question on overview of C# OOP in business WinForms application - scope of Object

  - by TimR

  I may have all this OO completely wrong, but here goes: Ok the scenario is a classic order entry. Customer places an Order which has OrderLineItems of StockItems. Order is entered by Employee. 1) Application starts and asks for login/password 2) Employee selects 'Orders' from Mainmenu form 3) Orders forms opens.... 4) Employee selects Customer 5) Employee selects Stock adds to OrderLineItems 6) Selects second StockItem; add to OrderLineItems 7) Order is committed, [stock decremented, order posted to DB, Order printed] 8) Employee is returned to MainMenu Now with Object scope: 1) Application starts and asks for login/password Is this the best place to make objEmployee, to be kept whilst in this whole Sales application? 2) Employee selects 'Orders' from Mainmenu form 3) Orders forms opens.... *Make objOrderHeader, is objEmployee able to be passed in or is it created here, or re-created here.* 4) Employee selects Customer - adds/edits Customer details if required... Make objCustomer 5) Employee selects Stock adds to OrderLineItems... *Make objStockItem and objOrderLineItem - add to objOrderLineItems_collection* 6) Selects second StockItem; add to OrderLineItems... *Make objStockItem and objOrderLineItem - add to objOrderLineItems_collection* 7) Order is committed, [stock decremented, order posted to DB, Order printed, Order Entered By = EmployeeID] Once posted to Db, all objects now redundant/garbage [except objEmployee?] 8) Employee is returned to MainMenu is objEmployee still valid as an object?

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• Javascript Canvas Drawing Efficiency

  - by jujumbura

  I have just recently started some experiments with game development in Javascript/HTML5, and so far it has been going pretty well. I have a simple test scene running with some basic input handling, and a hundred-ish drawImage() calls with a few transforms. This all runs great on Chrome, but unfortunately, it already chugs on Firefox. I am using a very large canvas ( 1920 x 1080 ), but it doesn't seem like I should be hitting my limit already. So on that note, I was hoping to ask a few questions: 1) What exactly is done on the CPU vs. the GPU in terms of canvas and drawImage()? I'm afraid the answer is probably "it depends on the browser", but can anybody give me some rules of thumb? I naively imagined that each drawImage call results in a textured quad on the GPU with the canvas effectively being a render target, but I'm wondering if I'm pretty far off base there... 2) I have seen posts here and there with people saying not to use the translate(), rotate(), scale() functions when drawing on the canvas. Am I adding a lot of overhead just by adding a translate() call, as opposed to passing in the x,y to drawImage()? Some people suggest using "transate3d", etc., which are CSS properties, but I'm not sure how to use them within a scene. Can they be used for animated sprites within a single canvas? 3) I have also seen a lot of posts with people mentioning that pre-building canvases and then re-using them is a lot faster than issuing all the individual draw calls again. I am guessing that my background should definitely be pre-built into a canvas, but how far should I take this? Should I maintain an individual canvas for each sprite, to cache all static image data when not animating? Thank you much for your advice!

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