[10] === 10    // is false
[10]  == 10    // is true
'10' == 10     // is true
'10' === 10    // is false
 []   == 0     // is true
 [] ===  0     // is false
 '' == false   // is true but true == "a" is false
 '' ===   false // is false

function Person(firstName, lastName){
    this.firstName =  firstName;
    this.lastName = lastName;
}
 
var Saad = new Person("Saad", "Mousliki");

var arr = ["a", "b", "c"];
typeof arr;   // return "object"
arr  instanceof Array // true
arr.constructor();  //[]

(function(){
    // some private code that will be executed automatically
})();
(function(a,b){
    var result = a+b;
    return result;
})(10,20)

var items = [12, 548 , 'a' , 2 , 5478 , 'foo' , 8852, , 'Doe' , 2145 , 119];
var  randomItem = items[Math.floor(Math.random() * items.length)];

x = Math.floor(Math.random() * (max - min + 1)) + min;

var numbersArray = [] , max = 100;
for( var i=1; numbersArray.push(i++) < max;);  // numbers = [0,1,2,3 ... 100]

function generateRandomAlphaNum(len) {
    var rdmstring = "";
    for( ; rdmString.length < len; rdmString  += Math.random().toString(36).substr(2));
    return  rdmString.substr(0, len);
}

var numbers = [5, 458 , 120 , -215 , 228 , 400 , 122205, -85411];
numbers = numbers.sort(function(){ return Math.random() ¨C 0.5});
/* the array numbers will be equal for example to
[120, 5, 228, -215, 400, 458, -85411, 122205] */

String.prototype.trim = function(){return this.replace(/^\s+|\s+$/g, "");};

var array1 = [12 , "foo" , {name: "Joe"} , -2458];
var array2 = ["Doe" , 555 , 100];
Array.prototype.push.apply(array1, array2);
/* array1 will be equal to  [12 , "foo" , {name "Joe"} , -2458 , "Doe" , 555 , 100] */

var argArray = Array.prototype.slice.call(arguments);

function isNumber(n){
    return !isNaN(parseFloat(n)) && isFinite(n);
}

function isArray(obj){
    return Object.prototype.toString.call(obj) === '[object Array]' ;
}

Array.isArray(obj); // ÕâÊÇÒ»¸öеÄarrayµÄ·½·¨

var myFrame = document.createElement('iframe');
document.body.appendChild(myFrame);
var myArray = window.frames[window.frames.length-1].Array;
var arr = new myArray(a,b,10); // [a,b,10]
// instanceof will not work correctly, myArray loses his constructor
// constructor is not shared between frames
arr instanceof Array; // false

var  numbers = [5, 458 , 120 , -215 , 228 , 400 , 122205, -85411];
var maxInNumbers = Math.max.apply(Math, numbers);
var minInNumbers = Math.min.apply(Math, numbers);

var myArray = [12 , 222 , 1000 ];
myArray.length = 0; // myArray will be equal to [].

var items = [12, 548 ,'a' , 2 , 5478 , 'foo' , 8852, , 'Doe' ,2154 , 119 ];
items.length; // return 11
delete items[3]; // return true
items.length; // return 11
/* items will be equal to [12, 548, "a", undefined ¡Á 1, 5478, 
"foo", 8852, undefined ¡Á 1, "Doe", 2154, 119]   */

var items = [12, 548 ,'a' , 2 , 5478 , 'foo' , 8852, , 'Doe' ,2154 , 119 ];
items.length; // return 11
items.splice(3,1) ;
items.length; // return 10
/* items will be equal to [12, 548, "a", 5478, 
"foo", 8852, undefined ¡Á 1, "Doe", 2154,119]   */

var myArray = [12 , 222 , 1000 , 124 , 98 , 10 ];
myArray.length = 4; // myArray will be equal to [12 , 222 , 1000 , 124].

myArray.length = 10; // the new array length is 10
myArray[myArray.length - 1] ; // undefined

var foo = 10;
foo == 10 && doSomething(); // µÈ¼ÛÓÚ if (foo == 10) doSomething();
foo == 5 || doSomething(); // µÈ¼ÛÓÚ if (foo != 5) doSomething();

function doSomething(arg1){
    Arg1 = arg1 || 10; // Èç¹ûarg1ûÓб»ÉèÖõĻ°£¬Arg1½«±»Ä¬ÈÏÉè³É10
}

var squares = [1,2,3,4].map(function (val) {
    return val * val;
});
// squares will be equal to [1, 4, 9, 16]

var num =2.443242342;
num = num.toFixed(4);  // num will be equal to 2.4432

0.1 + 0.2 === 0.3 // is false
9007199254740992 + 1 // is equal to 9007199254740992
9007199254740992 + 2 // is equal to 9007199254740994