Named anonymous functions vs anonymous functions

Question

So I am confused as to when I would use an anonymous function such as:

let foo = function () {
  //code
}

versus a named anonymous function such as:

let foo = function foo () {
  //code
}

Besides browser support, namely IE, are there any differences between the two? When should I use one over the other?

Answer 1

In this case, where the function declaration name is the same as the variable it is assigned to, it doesn't make much difference.

If you used a different name for the definition and assignment, the name on the right takes precedence in naming the function:

foo = function bar() {}
foo.name  // "bar"

In both cases you assign your function to a variable (function expression), but in the first case you assign an unnamed/anonymous function, whereas in the second case you assign a named function. When assigning an anonymous function to a variable in such a simple expression, the JS engine is able to name the function properly.

Consider the following case where this assignment is non-obvious for the engine:

function p(fun) { return fun; }
foo = p(function() {})
foo.name  // empty string

TL;DR; with named functions you often get better stack traces.