Demo how variable declarations are hoisted. Regardless of where they occur in the function scope, it will be hoisted to the top. That's why all the variables should be declare at the top.

js-hoist.js

// Regardless of where they occur in the function scope,
// it will be hoisted to the top.
// it looks like this

var foo = 1;

function bar() {
	if (!foo) {
		var foo = 10;
	}
	alert(foo);
}

bar();
// => alert 10