What is the difference between naming functions or not in javascript?

Question

What is the difference between

settings = {
  edit: function (key, value) {
    return anotherFunction(key, value) {
      return value * 2;
    };
  }
};

and

settings = {
  edit: function edit(key, value) {
    return anotherFunction(key, value) {
      return value * 2;
    };
  }
};

?

possible duplicate of [What is the difference between a function expression vs declaration in Javascript?](http://stackoverflow.com/questions/1013385/what-is-the-difference-between-a-function-expression-vs-declaration-in-javascrip) — Barmar, Jan 12 '14 at 04:46

score 3 · Answer 1 · answered Jan 12 '14 at 04:45

3

There's no difference when executing.

However, in the second case (named function), you can call the function recursively easier because it has a name.

For example, with a named function you can do:

fact: function factorial(n) {
     if(n == 0) return 1;
     return n * factorial(n-1);   //You can do this with a named function easily
  }

Without a name, this would be tricky.

Cheers

answered Jan 12 '14 at 04:45

Edgar Villegas Alvarado

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Err, without a name, it'd be pretty easy: `this.fact()`. You can easily call a function without naming it: `var x = function() { x() }`. – user229044 Jan 12 '14 at 05:04
@meagar What if the function isn't part of an object? – Edgar Villegas Alvarado Jan 12 '14 at 05:05
`var x = function() { x() }` – user229044 Jan 12 '14 at 05:06
In this case `callback(function f(n){ f(...); });` it's much easier with a named function (the other option(s) would be harder) – Edgar Villegas Alvarado Jan 12 '14 at 05:09
"Much" easier is pretty subjective; `f = function () { return f(...); }; callback(f);` – user229044 Jan 12 '14 at 05:10
Yep, it might be subjective. For me, and I think for the 95% of the devs, mine is cleaner and easier (it's one sentence less), but more than that, _preferred_ – Edgar Villegas Alvarado Jan 12 '14 at 05:14

score 1 · Accepted Answer · answered Jan 12 '14 at 04:42

1

The essential difference is better debugging. In your developer tools, the named function in your second example will appear as edit in a backtrace; your first example will appear as anonymous. This can be extremely confusing when you're 10 function deep, and they are all called anonymous.

answered Jan 12 '14 at 04:42

user229044

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This is a very good observation. I'm trying to analyze Ghost.js to see how a node application works and this might be the best reason the functions are named. – Adam S Jan 12 '14 at 04:55
1

It really is. Everybody talking about recursion has missed the point. You don't need a *named* function to recurse, you just need a variable referencing the function. You can still recursively call an anonymous function this way. – user229044 Jan 12 '14 at 05:07

score 0 · Answer 3 · answered Jan 12 '14 at 04:54

There are three reasons to give a function an inherent name. The first is that everyone does it. It's what everyone is used to.

function factorial(n) {
    var accum = 1, i;
    for (i = 1; i <= n; i++) {
        accum *= i;
    }
    return accum;
}

The second is to understand stack traces better, as @meagar wrote.

The third is to let you write call functions recursively.

var factorial = function(n) {
    var a = 1;
    return (function factRecursive(k, a) {
        if (k >= 2) {return factRecursive(k - 1, k * a)}
        else        {return a;}
    })(n, a);
}

What is the difference between naming functions or not in javascript?

3 Answers3