Question

The following javascript works in Chrome and IE but errors out in Firefox because bar is undefined when assigned to callBar.

So who got their scope rules right?

function foo() {

    var callBar = bar;

    if (1 === 1) {
       callBar();
       function bar() {
          alert('yo');
       }
    }
}

foo();

Answer 1

Not sure who got it “right” according to the ECMA spec, but it doesn’t really matter since you can’t do this in all browsers and have to change your code 🙂

The simple explanation is that functions in if statement’s aren’t technically allowed and browsers do weird things with them. Some browsers treat this as an expression, others as a declaration. FF apparently treats it as an expression meaning it doesn’t exist until the code gets to that point. A detailed write-up is available at http://kangax.github.com/nfe/