var foo = (12.4 / 4.13) | 0;//結(jié)果為3
var bar = ~~(12.4 / 4.13);//結(jié)果為3

var eee="eee";
alert(!!eee)

(function() {
    var oldAlert = window.alert,
        count = 0;
    window.alert = function(a) {
        count++;
        oldAlert(a + "\n You've called alert " + count + " times now. Stop, it's evil!");
    };
})();
alert("Hello Haorooms");

var a=1,b=2;a=[b,b=a][0];
console.log('a:'+a+',b:'+b);

 //輸出a:2,b:1

[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(name, age) {
    this.getName = function() { return name; };
    this.setName = function(newName) { name = newName; };
    this.getAge = function() { return age; };
    this.setAge = function(newAge) { age = newAge; };

    //未在構(gòu)造函數(shù)中初始化的屬性
    var occupation;
    this.getOccupation = function() { return occupation; };
    this.setOccupation = function(newOcc) { occupation = 
                         newOcc; };
}

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)];

var 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);
}

//調(diào)用方法generateRandomAlphaNum(15);

var numbers = [5, 458 , 120 , -215 , 228 , 400 , 122205, -85411];
numbers = numbers.sort(function(){ return Math.random() - 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 isArray(obj){
    return Object.prototype.toString.call(obj) === '[object Array]' ;
}

Array.isArray(obj); // 這是一個(gè)新的array的方法

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 × 1, 5478, "foo", 8852, undefined × 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 × 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(); // 等價(jià)于 if (foo == 10) doSomething();
foo == 5 || doSomething(); // 等價(jià)于 if (foo != 5) doSomething();

function doSomething(arg1){
    Arg1 = arg1 || 10; // 如果arg1沒(méi)有被設(shè)置的話，Arg1將被默認(rèn)設(shè)成10
}

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

for (var name in object) {
    if (object.hasOwnProperty(name)) {
        // do something with name
    }
}

var a = 0;
var b = ( a++, 99 );
console.log(a);  // a will be equal to 1
console.log(b);  // b is equal to 99

var navright = document.querySelector('#right');
var navleft = document.querySelector('#left');
var navup = document.querySelector('#up');
var navdown = document.querySelector('#down');

isFinite(0/0) ; // false
isFinite("foo"); // false
isFinite("10"); // true
isFinite(10);   // true
isFinite(undifined);  // false
isFinite();   // false
isFinite(null);  // true  !!!

var numbersArray = [1,2,3,4,5];
var from = numbersArray.indexOf("foo") ;  // from is equal to -1
numbersArray.splice(from,2);    // will return [5]

var person = {name :'Saad', age : 26, department : {ID : 15, name : "R&D"} };
var stringFromPerson = JSON.stringify(person);
/* stringFromPerson is equal to "{"name":"Saad","age":26,"department":{"ID":15,"name":"R&D"}}"   */
var personFromString = JSON.parse(stringFromPerson);
/* personFromString is equal to person object  */

var func1 = new Function(functionCode);
var func2 = eval(functionCode);

var sum = 0;
for (var i in arrayNumbers) {
    sum += arrayNumbers[i];
}

var sum = 0;
for (var i = 0, len = arrayNumbers.length; i < len; i++) {
    sum += arrayNumbers[i];
}

for (var i = 0; i < arrayNumbers.length; i++)

setInterval('doSomethingPeriodically()', 1000);
setTimeOut('doSomethingAfterFiveSeconds()', 5000)

setInterval(doSomethingPeriodically, 1000);
setTimeOut(doSomethingAfterFiveSeconds, 5000);

function getCategory(age) {
    var category = "";
    switch (true) {
        case isNaN(age):
            category = "not an age";
            break;
        case (age >= 50):
            category = "Old";
            break;
        case (age <= 20):
            category = "Baby";
            break;
        default:
            category = "Young";
            break;
    };
    return category;
}
getCategory(5);  // will return "Baby"

function clone(object) {
    function OneShotConstructor(){};
    OneShotConstructor.prototype= object;
    return new OneShotConstructor();
}
clone(Array).prototype ;  // []
四十二、一個(gè)HTML轉(zhuǎn)義函數(shù)
function escapeHTML(text) {
    var replacements= {"<": "<", ">": ">","&": "&", "\"": """};
    return text.replace(/[<>&"]/g, function(character) {
        return replacements[character];
    });
}

var object = ['foo', 'bar'], i;
for (i = 0, len = object.length; i <len; i++) {
    try {
        // do something that throws an exception
    }
    catch (e) {
        // handle exception
    }
}

var object = ['foo', 'bar'], i;
try {
    for (i = 0, len = object.length; i <len; i++) {
        // do something that throws an exception
    }
}
catch (e) {
    // handle exception
}

var xhr = new XMLHttpRequest ();
xhr.onreadystatechange = function () {
    if (this.readyState == 4) {
        clearTimeout(timeout);
        // do something with response data
    }
}
var timeout = setTimeout( function () {
    xhr.abort(); // call error callback
}, 60*1000 /* timeout after a minute */ );
xhr.open('GET', url, true);  

xhr.send();

var timerID = 0;
function keepAlive() {
    var timeout = 15000;
    if (webSocket.readyState == webSocket.OPEN) {
        webSocket.send('');
    }
    timerId = setTimeout(keepAlive, timeout);
}
function cancelKeepAlive() {
    if (timerId) {
        cancelTimeout(timerId);
    }
}

var min = Math.min(a,b);
A.push(v);

var min = a < b ? a b;
A[A.length] = v;

function paddingLeftZero(str){
    return ("00"+str).substr(str.length);
}

getCookie: function (name) {
    var arr, reg = new RegExp("(^| )" + name + "=([^;]*)(;|$)");

    if (arr = document.cookie.match(reg))
        return unescape(arr[2]);
    else
        return null;
},
setCookie: function (name, value, Days) {
    var exp = new Date();
    exp.setTime(exp.getTime() + Days * 24 * 60 * 60 * 1000);
    document.cookie = name + "=" + escape(value) + ";expires=" + exp.toGMTString();
},

new Date(new Date(new Date().toLocaleDateString()).getTime()+24*60*60*1000);

new Date(new Date(new Date().toLocaleDateString()).getTime());