Why does local variable names take precedence over function names in JavaScripts?
- by fredrik
In JavaScript you can define function in a bunch of different ways:
function BatmanController () {
}
var BatmanController = function () {
}
// If you want to be EVIL
eval("function BatmanController () {}");
// If you are fancy
(function () {
function BatmanController () {
}
}());
By accident I ran across a unexpected behaviour today. When declaring a local variable (in the fancy way) with the same name as function the local variable takes presence inside the local scope. For example:
(function () {
"use strict";
function BatmanController () {
}
console.log(typeof BatmanController); // outputs "function"
var RobinController = function () {
}
console.log(typeof RobinController); // outputs "function"
var JokerController = 1;
function JokerController () {
}
console.log(typeof JokerController); // outputs "number", Ehm what?
}());
Anyone know why var JokerController isn't overwritten by function JokerController? I tested this in Chrome, Safari, Canary, Firefox. I would guess it's due to some "look ahead" JavaScript optimizing done in the V8 and JägerMonkey engines. But is there any technical explanation to explain this behaviour?
