Javascript 'delete' doesn't work inside iteration loop

I'm a C/C++/Java programmer working with JavaScript.

I'm trying to write a function that will delete all properties of an object 'obj'. I've read the posting on "How to quickly clear a Javascript Object?" and saw that there are two answers: (1) creating a new 'obj' (which I don't want to do because my code is a high-performance program running in a mobile browser, and I want to minimize garbage collection); and (2) iterating over the properties of an object in a loop and deleting the properties. This latter approach doesn't work in Chrome 12.

Consider th开发者_如何学Pythone following code:

var foo = {};
foo['baz'] = 'bar';
console.log("1. foo.baz = " + foo.baz);

delete foo.baz;
console.log("2. foo.baz = " + foo.baz);

foo['baz'] = 'bar';
console.log("3. foo.baz = " + foo.baz);

for (prop in foo)
{
    if (foo.hasOwnProperty(prop))
    {
        console.log("deleting property " + prop);
        delete foo.prop;
    }
}
console.log("4. foo.baz = " + foo.baz);

This produces the following result in my console on Chrome 12:

1. foo.baz = bar
2. foo.baz = undefined
3. foo.baz = bar
deleting property baz
4. foo.baz = bar

Why doesn't foo.baz get deleted inside the loop?

You lookup the key in the wrong way. You need to use the bracket notation:

delete foo[ prop ];

However, you don't need to loop over every property within an object. It's just fine to null the object reference itself. The garbage collector will take care of you.

foo = null; // done

Talking of high performance, that is the way you want to do.

This line delete foo.prop is incorrect. foo has no property named prop in this case. Using brackets delete foo[prop].

Because foo.prop never was defined to delete. You need to delete it like this:

delete foo[prop];

Try this instead:

delete foo[prop];

HTH