Tuesday, 24 June 2014

Javascript and garbage collection

Javascript doesn't have explicit memory mangament, it's the browser which decides when to clean it up. Sometimes it may happen that you experience unsmooth rendering of JavaScript due to a garbage collection pause.
There are many techniques that you can apply to overcome glitches caused by garbage collection (GC). More you apply more you explore. Suppose you have a game written in JavaScript , and every second you are creating a new object then its obvious that at after certain amount of time GC will occur to make further space for your application.
For real time application like games, which requires lot of space the simplest thing you can do is to reuse the same memory. It depends on you how you structure your code. If it generates lots of garbage then it might give choppy experience.

By using simple procedures: This is well know that new keyword indicates allocation. Wherever possible you can try to reuse the same object by each time by adding or modifying properties. This is also called recycling of object
In case of Arrays, assigning [] is often used to clear array, but you should keep in mind that it also creates a new array and garbages the old one. To reuse the same block you should use arr.length = 0 This has the same effect but it reuses the same array object instead of creating new one.
In case of functions: Sometimes our program needed to call a specific function more time or on certain intervals by using setInterval or setTimeout.
ex: setTimeout(function() { doSomething() }, 10);
You can optimize the above code by assigning the function to a permanent variable rather than spawning each time at regular intervals.
    ex : var myfunc = function() { doSomething() }
    setTimeout(myfunc, 10);
Other possible thing is that, the array slice() method returns a new array (based on a range in the original array,that can remain untouched), string's substr also returns a new string (based on a range of characters in the original string, that can remain untouched), and so on. Calling these functions creates garbage if not reutilized properly.
To avoid garbage completely in JavaScript is very difficult, you could say impossible. Its depends, how you reuse the objects and variables to avoid garbage. If your code is well structured and optimized you can minimize the overhead.

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