Types in Javascript（jQuery）

String: 空字符串等于Boolean的false;

htmlString: 包括起始tag和结束tag的字符串，代表html代码；

Number：双精度64位，跟string一样属于immutable，基于c语言的运算符都适用于此值；0默认为false，!0为true；

Math函数，parseInt函数（各进制到int的转换）；

转换为字符串，""+1+2==“12”，""+（1+3）==“4”......

NaN，非Number的对象会返回NaN，用isNaN函数判断；Number类型；

Infinity，1/0==infinity；Number类型；

                Note：NaN==NaN is false，Infinity==Infinity is true；

                Integer属于Number类型，必须为非浮点数；

Float属于Number类型，为浮点数；

Boolean: true or false;

Object:  var x = {}; {}的类型为object，默认值false；

var y = {name: "Pete",age: 15};

使用dot访问对象的属性：y.name or y.age;

使用array索引访问，y[name],y[age]

迭代for(key in y){ //do sth with key, and access value using y[key]}；

Note：使用其他library的时候，可能扩展了Object.prototype，so take care！如：jQuery.each(obj,function(key,value))){}

Note:javascript对象没有继承机制，a workaround是使用prototype满足继承关系：

var Employee = function(name, title) {                                                                      this.name = name;                                                                      this.title = title;                                                                      this.greet = function() {                                                                                         if (this.canTalk) {                                                                                                                        console.log("Hi, I'm "+this.name+", the "+this.title);                                                                                                                   }                                                                                                           }                                                                                           }                         var Customer = function(name) {this.name = name;}                         var Mime = function(name) {this.name = name;this.canTalk = false;}                         var Person = {

canTalk : true,

greet : function() {                                                                                    if (this.canTalk) {console.log("Hi, I'm "+this.name)}

}                                                 }

继承机制为prototype；                        Customer.prototype = Person;                        Employee.prototype = Person;                       Mime.prototype = Person;                       var bob = new Employee('Bob','Builder');              var joe = new Customer('Joe');              var rg = new Employee('Red Green','Handyman');              var mike = new Customer('Mike');              var mime = new Mime('Mime');              bob.greet();              joe.greet();              rg.greet();              mike.greet();              mime.greet(); Array: var x=[]; var y=[1,2,3];数组的类型为object，使用索引读写数组；无论空否，数组默认为true；

数组迭代使用y=a.length作为终止条件，只读一次属性，速度比使用a.length作为终止条件快；

for ( var i = 0, item; item = a[i]; i++ ) {// Do something with item}此时数组不能为空；

var x=[1,2,3]; jQuery.each(x,function(index,value){//do sth with index and value});

var x=[]; x.push(1); x[x.length]=2;  x is [1,2];

support method: reverse, join, shift, etc.

Array<Type>在Jquery中表示方法需要的参数类型是数组，且元素类型是指定值；

PlainObject： jQuery.isPlainObject(object)判断对象是否由{}或new Object(){}创建；

Function:  命名函数和匿名函数；

Arguments

function log( x ) {console.log( typeof x, arguments.length );}                     log(); // "undefined", 0                     log( 1 ); // "number", 1                     log( "1", "2", "3" ); // "string", 3

Note：上面的log函数体中，arguments变量总是有效的，arguments变量有length,callee(调用者)等属性；

                    var awesome = function(){return arguments.callee;}

                    awesome()==awesome   //true;

                  Context,Call,Apply

"this"引用当前context，默认引用window对象，在function中可以改变context；

Function.prototype.call() and Function.prototype.apply(); refer to here and here.

                     NOTE: call和apply的异同：1.无参数时两者无区别；2.函数带参数时候，call(this,argumentsList)，而apply (this,argumentArray);

                  Scope: 变量的作用域；

                  Closures:

                        function create() {                                                          var counter = 0;                                                          return {

increment: function() {counter++;},

print:function() {console.log( counter );}

}                                                      }                         var c = create();                         c.increment();                         c.print();                         The pattern allows you to create objects with methods that operate on data that isn't visible to the outside—the very basis of object-oriented programming.

Proxy Pattern

Callback: 

                  Callback is a plain JavaScript function, or sometimes just an event;

                  $( "body" ).click(function( event ) {                            console.log( "clicked: " + event.target );

                                                                      });                   Some callbacks are required to return something, others make that return value optional. To prevent a form submission, a submit event handler can return false:

$( "#myform" ).submit(function() { return false; }); selector: some plugin will leverage jQuery's selector.

for instance, validation plugin accepts a selector to specify a dependency, whether an input is required or not:

emailrules:{required:"#email:filled"}

Events: blur,focus, load, resize, scroll, unload, beforeunload, click, dblclick, mousedown, mouseup, mousemove, mouseover, mouseout, mouseenter, mouseleave, change, select, submit, keydown, keypress,and keyup.

jQuery: jquery object is a collection of DOM elements, it behaves much like an array but not actually a Javascript Array;

you will use the jQuery() function to create a jQuery object. jQuery() can also be accessed by its familiar single-character alias of $(), unless you have called jQuery.noConflict() to disable this option. Many jQuery methods return the jQuery object itself, so that method calls can be chained:

$( "p" ).css( "color", "red" ).find( ".special" ).css( "color", "green" ); 会对jQuery对象进行筛选，如find()，这些操作会返回一个经过筛选的新的jQuery对象；需要返回前一个jQuery对象则用.end(). 出的jQuery对象为empty，则最后的操作对DOM没有影响。 XMLHttpRequest： 有些AJAX返回XHR object，或者作为参数传递给success/error/complete hanlders，可以在其他操作中使用这个对象。 NOTE:Ajax只有在request使用此对象的情况下才返回该对象。

jqXHR: 从jquery1.5开始，$.ajax()返回jqXHR对象，which is a superset of the XMLHTTPRequest object.

Deferred Object（延迟对象）: 使用自我管理的callback queues注册多个callback，按需调用。

Promise Object：此对象提供延迟对象的方法子集(then,done,fail,always,pipe,isResolved,isRejected)，防止用户更改延迟对象。

Callbacks Object：使用方法$.Callbacks()来create或者返回Callbacks对象，此对象用途广泛，比较强大的功能是用来管理callback lists。

XML Object：一个由浏览器的XML DOM parser创建的文档对象，一般来自一个代表XML的字符串，XML文档与HTML语法不同，但jQuery的大多数遍历或操作都适用于此对象(XML文档)。

仅作个人学习只用，转载注明原文出处，引自：http://api.jquery.com/Types/