for (prop in object) or indexed for loop?

[Raffles]

I have this function which does things to something in an object:

dostuff(p) {
  for (prop in Thing) if (prop == p) Thing[prop].className = 'x';
}

which seems nice and clean. But if there is more than one argument, I can end up doing stuff like this:

dostuff(a,b,c) {
  for (prop in Thing) if (prop == a || prop == b || prop == c) Thing[prop].className = 'x';
}

If there is more than one argument, should I just be using a "normal" for loop:

dostuff() {
  for (var i = 0; i < arguments.length; i++) Thing[arguments[i]].className = 'x';
}

? Or is there some other thing that one can do that I'm missing?

[Kravvitz]

Well, what is Thing? Is it an array or a NodeList? Or is it some other kind of object?

[Raffles]

It's an object, to avoid using global variables. Most of the object's properties are references to elements or constants used throughout the script. In this case, the arguments for dostuff() are of the sort Thing.box, which is a reference to an HTML element.

[Kravvitz]

Are you planning on passing the class as an argument, are you hard coding that, or is that just an example of what the function might do?

[Raffles]

The class is hardcoded, the only things that get passed as arguments are properties of Thing (as strings).

[Kravvitz]

Since IE versions before 5.5 don't support the "in" operator, I suggest you use the following, which is like the third function you posted, except it makes sure that the sub-object of Thing exists before trying to change a property of it.

function doStuff() {
  for(var i=0,l=arguments.length;i<l;i++){
    if(typeof(Thing[arguments[i]]) != 'undefined')
      Thing[arguments[i]].className = 'x';
  }
}

[Raffles]

Thanks Kravvitz, I thought it would be that. forEach would be nice, but nobody supports it except Mozilla.

[Kravvitz]

You're welcome

You can add support for it via Array.prototype. I'm not sure why you think it would be better for this though.

[Raffles]

It's just because I've got used to using it PHP and I like the way it works. Adding it to Array is not worth the trouble and I've read in a couple of places that in general extending the Array object is bad practice.

[Kravvitz]

JavaScript's forEach() is very different from PHP's foreach(). (Read the page I linked to to see for yourself.)

JavaScript's for-in loop is the functional equivalent of PHP's foreach().