Hey for those who think they really know javascript, what do you think the following code will do:

var foo = 1;
function bar() {
    if(!foo) {
        var foo = 10;
    }
    console.log(foo);
}
bar();

Then, run the following
http://jsfiddle.net/dodozhang21/NaLxn/
Were you expecting 1? so WTF?

Look up javascript hoisting