Question

I never really gave much thought to garbage collection and I don’t know whether or not it is necessary to take into account when making small javascript games/applications. Any advice is appreciated, but I will ask my specific question at the end.

A lot of the time I write code of this form:

var foos=new Array();
generateFoos();
function generateFoos()
{
    foos=[];
    for (fooIndex=0;fooIndex<numberOfFoos;fooIndex++)
    {
        foos[fooIndex]=new foo(Math.random(),Math.random());
    }
} 
function foo(bar,bas)
{
   this.bar=bar;
   this.bas=bas;
}

So my question is, when I say foos=[] (line 5), does this delete the objects in that array from the memory or do they float around somewhere, making the program larger and slower? What should I do if I want to call generateFoos() a loooot of times, like every time the user presses a key.

Thanks!

Answer 1

For a specific answer, since the accepted one doesn’t actually answer the question directly, is that yes, foo = [] does de-reference any previous values in the array.

As Ales says, “An object becomes eligible for garbage collection when it becomes unreachable.” Indeed, this is when the browser will clear such things from memory.

An important point, delete DOES NOT GARBAGE COLLECT.

You see this over and over, and even in the comments on this question. The delete keyword removes a property from an object and has nothing to do with garbage collection.

I also wanted to offer some advice on your code itself.

1) Use literals, not new, for basic data types

2) Don’t call functions before you declare them. Yes, it works but its messy and harder to read later. Remember, you spend much more time reading your code than writing it. Make it easy to follow later.

3) Remember your function scope. Any variable declared without var goes global. With var, it remains within the scope of the function that contains it. Another way variables are scoped within a function is when they are passed in as named parameters.

4) Use var on your functions when creating them. In your code, your functions are globals.

5) Use spacing. Density of text is not next to godliness. You might be 20-something now with great eyesight, but you’ll appreciate white space in just a very few short years.

6) Declare counters in for loops with var. Unless you want them to be global. And you almost never will.

Lets re-work your code now:

var numberOfFoos = 10,
    foos = [];

var generateFoos = function(){

    foos = [];

    for( var fooIndex = 0; fooIndex < numberOfFoos; fooIndex++ ){

        foos[ fooIndex ] = new foo( Math.random(), Math.random() );

    }

},

foo = function( bar, bas ){

   this.bar = bar;
   this.bas = bas;

}

generateFoos();
console.log( foos );