Why use named function expressions?

Question

We have two different way for doing function expression in JavaScript:

Named function expression (NFE):

var boo = function boo () {         


        

Answer 1

Naming functions is useful if they need to reference themselves (e.g. for recursive calls). Indeed, if you are passing a literal function expression as an argument directly to another function, that function expression cannot directly reference itself in ES5 strict mode unless it is named.

For example, consider this code:

setTimeout(function sayMoo() {
    alert('MOO');
    setTimeout(sayMoo, 1000);
}, 1000);

It would be impossible to write this code quite this cleanly if the function expression passed to setTimeout were anonymous; we would need to assign it to a variable instead prior to the setTimeout call. This way, with a named function expression, is slightly shorter and neater.

It was historically possible to write code like this even using an anonymous function expression, by exploiting arguments.callee...

setTimeout(function () {
    alert('MOO');
    setTimeout(arguments.callee, 1000);
}, 1000);

... but arguments.callee is deprecated, and is outright forbidden in ES5 strict mode. Hence MDN advises:

Avoid using arguments.callee() by either giving function expressions a name or use a function declaration where a function must call itself.

(emphasis mine)