JavaScript Tips – Switching from ActionScript to JavaScript: Tips for Writing Code

First, the "self-calling functions" aren't actually self-calling. I know that's what people in the Javascript community call them, but it's really misleading; the functions never reference themselves, and in fact a lot of the time there's no way to call that particular function more than once. If they were actually self-calling functions, then recursive functions would have been the best way to name them.

What you really have are (usually) immediately executed lambdas whose results are stored in a variable in order to limit the scope of their internals. "IEL" isn't as catchy as "self-calling functions", so I guess that's why the real name never caught on.

The thing is though, that's entirely too low-level; it's an implementation detail that nobody cares about (it's like saying "here be for loops"). Generally, when you're using those immediate-execution functions, the reason why you're using them is because you're making some sort of a module, which needs its own namespace.

If that's the case, then instead of saying "self-executing functions", you should say "this script contains modules that do <stuff>". Otherwise, you should figure out what you're trying to do with the functions, and say that's what's in your script.

Now, the reason why you use modules in Javascript is because otherwise everything goes into the global scope. Those other functions you're writing, that aren't going to be inside the modules (or whatever you decide they are), are going to end up there. So use that - "this script file contains both modules that do <stuff> and global functions that do <more stuff>".

Which do you think looks cleaner?

object = new Array();
object.prop1 = 1;
object.prop2 = 2;
object.prop3 = 3;

or

object = {
  prop1: 1,
  prop2: 2,
  prop3: 3
}

?

Also, if you do something like this:

if (object.length === undefined) object.length = 10
object.length // 0

Then object.length will still be 0, which is definitely not what you would expect. You might think this is just a fake example that will never come up in real life, but look at this:

words = 'You should join our club because it is a club'.split(' ')
obj = new Array()
words.forEach(function(x) {
  if (obj[x] === undefined) obj[x] = 0
  obj[x] ++
})
for (var x in obj) console.log(x, obj[x])

This will log:

You 1
should 1
join NaN // <-- oops
our 1
club 2
because 1
it 1
is 1
a 1

Alternatively, you could make an analogy to any other object, like a function:

object = function() {}
object.prop1 = 1;
// ...

Anyone could immediately tell you that that is wrong, and using an array is just as wrong.