pseudosavant

var global = (function(g) {
    return g;
})(this);

global.a = 'Hello World';
console.log(a); // 'Hello World'

pseudosavant

(function(global){
    var x = 2,
        y = Math.pow(x, 2);
    
    global.z = y;
})(this);

console.log(x); // undefined
console.log(y); // undefined
console.log(z); // 4

pseudosavant

(function(global){
    var who = 'World';
    
    var rename = function(s) {
        who = s;
    };
    
    var welcome = function(){
        return 'Hello ' + who;
    };

pseudosavant

var welcome = function(name) {
    name = name || 'World';
    return 'Hello ' + name;
};

console.log(welcome()); // 'Hello World'
console.log(welcome('foo')); // 'Hello foo'

pseudosavant

// jQuery
var $myFormButton = $('.myForm input[type=button]'); // Potentially slow query

$myFormButton.val('Submit');
// lots of code later
$myFormButton.val('Processing'); // Didn't need to lookup the element(s) again
$myFormButton.attr('disabled', true); // Didn't need to lookup the element(s) again


// DOM

pseudosavant

// jQuery
var $myForm = $('#myForm');

// Find child elements in the form without searching the entire DOM
$myForm.children('input[type=text]').focus();
$myForm.children('input[type=button]').val('Submit');


// DOM
var $myForm = document.querySelector('#myForm');

pseudosavant

// Convert a set of DOM elements to an array
var domElements = document.querySelectorAll('li');
console.log(domElements.pop()); // Undefined

var arrayOfDomElements = Array.prototype.slice.apply(domElements);
console.log(arrayOfDomElements.pop()); // [object HTMLLIElement]


// Convert function arguments to an array
var myFunction = function() {

pseudosavant

var obj = {
        welcome: 'Hello',
        name: 'World'
    },
    value;

for (var prop in obj) {
    // Check if the object has that property so that prototypes aren't included.
    if(obj.hasOwnProperty(prop)) {
        value = obj[prop];

pseudosavant

var myArray = [
    'Hello',
    'World',
    'foo',
    'bar'
];

// Only check the `length` property once by setting `l` at the same time as `i`.
for (var i = 0, l = myArray.length; i < l; i++) {
    console.log(myArray[i]);

pseudosavant

var myArray = [
    'Hello',
    'World',
    'foo',
    'bar'
    ];
 
// Only check the `length` property once by setting `l` at the same time as `i`.
for (var i = 0, l = myArray.length; i < l; i++) {
    console.log(i);