Function was used before it was defined - JSLint

Question

JSLint does not like this code saying \"\'b\' was used before it was defined\"

var a = function () {
        b();
    },

    b = function () {
        alert         


        

Answer 1

So why is JSLint doing this? Is there a reason I should be declaring all my functions first?

Yes, otherwise there might be some unexpected errors. Your code works because of JavaScript's "Hoisting". This mechanism pulls up all declarations, implicit or explicit and can cause some unexpected results.

Consider this code:

var s = "hello";    // global variable
function foo() {
    document.write(s);   // writes "undefined" - not "hello"
    var s = "test";      // initialize 's'
    document.write(s);   // writes "test"
};
foo();

It's being interpreted as follows:

var s = "hello";    // global variable
function foo() {
    var s;               // Hoisting of s, the globally defined s gets hidden
    document.write(s);   // writes "undefined" - now you see why
    s = "test";          // assignment
    document.write(s);   // writes "test"
}
foo();

(example taken from the german Wikipedia page: http://de.wikipedia.org/wiki/Hoisting)