Question

I wrote the following code to “pop” a property from an object as if it were an array. This looks like the kind of code that would get me slapped by more serious programmers, so I was wondering what is the proper way to do this:

// wrong way to pop:
for( key in profiles ){
    var profile = profiles[key];  // get first property
    profiles[key] = 0;            // Save over property just in case "delete" actually deletes the property contents instead of just removing it from the object
    delete profiles[key];         // remove the property from the object
    break;                        // "break" because this is a loop
}

I should have mentioned above, that unlike a true “pop”, I don’t need the objects to come out in any particular order. I just need to get one out and remove it from its parent object.

Answer 1

for( key in profiles ){

You should really declare key as a var.

profiles[key] = 0;            // Save over property just in case "delete" actually deletes the property contents instead of just removing it from the object

is unnecessary. Delete doesn’t touch the value of the property (or in the case of a property that has a setter but no getter, even require that it have a value).

If the object has any enumerable properties on its prototype, then this will do something odd.
Consider

Object.prototype.foo = 42;

function take(obj) {
  for (var key in obj) {
    // Uncomment below to fix prototype problem.
    // if (!Object.hasOwnProperty.call(obj, key)) continue;
    var result = obj[key];
    // If the property can't be deleted fail with an error.
    if (!delete obj[key]) { throw new Error(); }
    return result;
  } 
}

var o = {};
alert(take(o));  // alerts 42
alert(take(o));  // still alerts 42