Quick JS file demonstrating closures very simply

closure.js

var foo = 100;

console.log('first'); //=> 'first'
console.log(foo);     //=> 100

(function () {
    var foo = 200;

    console.log('second'); //=> 'second'
    console.log(foo);      //=> 200
}());

console.log('third'); //=> 'third'
console.log(foo);     //=> 100

closures2.js

var foo = 100;

console.log('first'); //=> 'first'
console.log(foo);     //=> 100

function test() {
    var foo = 200;

    console.log('second'); //=> 'second'
    console.log(foo);      //=> 200
}
test();

console.log('third'); //=> 'third'
console.log(foo);     //=> 100

closures3.js

var foo = 100;

console.log(foo);     //=> 100

function test() {
    console.log(foo); //=> 100
}
test();

(function () {
    console.log(foo); //=> 100
}());

console.log(foo);     //=> 100

closures4.js

var foo = 100;

console.log(foo);     //=> 100

(function () {
    var bar = 200;
    console.log(foo); //=> 100
    console.log(bar); //=> 200
}());

console.log(foo);     //=> 100
console.log(bar);     //=> ERROR

On the first example like you saw $foo will use the values define on its own scope.

On the second example on https://gist.github.com/Greduan/48bb89dd54dbd9cf5c83#file-closures2-js-L15 the value will be 200. This is what I ready on the script, I will run it