jQuery extend()详解及简单实例

$.get(); 
$.post(); 
$.getJSON(); 

$('div').css(); 
$('ul').find('li'); 

$('li').each(callback); 
$.each(lis,callback); 

functionA(){ 
     
  } 
  A.prototype.fun_p=function(){console.log("prototpye");}; 
  A.fun_c=function(){console.log("constructor");}; 
  var a=new A(); 
  A.fun_p();//A.fun_p is not a function 
  A.fun_c();//constructor 
  a.fun_p();//prototpye 
  a.fun_c();//a.fun_c is not a function 

functionA(){ 
    this.fun_f=function(){ 
        console.log("Iam in the constructor"); 
    }; 
} 
A.prototype.fun_p=function(){ 
    console.log("Iam in the prototype"); 
}; 
var a=newA(); 
a.fun_f();//Iam in the constructor 
a.fun_i=function(){ 
    console.log("Iam in the instance"); 
}; 
a.fun_i();//Iam in the instance 
a.fun_p();//Iam in the prototype 

jQuery.extend = jQuery.fn.extend = function() { 
    var options,name, src, copy, copyIsArray, clone, 
        target= arguments[0] || {}, 
        i =1, 
        length= arguments.length, 
        deep= false; 
    // Handle adeep copy situation 
    if ( typeoftarget === "boolean" ) { 
        deep= target; 
        //Skip the boolean and the target 
        target= arguments[ i ] || {}; 
        i++; 
    } 
    // Handlecase when target is a string or something (possible in deep copy) 
    if ( typeoftarget !== "object" && !jQuery.isFunction(target) ) { 
        target= {}; 
    } 
    // ExtendjQuery itself if only one argument is passed 
    if ( i ===length ) { 
        target= this; 
        i--; 
    } 
    for ( ; i< length; i++ ) { 
        //Only deal with non-null/undefined values 
        if ((options = arguments[ i ]) != null ) { 
            //Extend the base object 
            for( name in options ) { 
                src= target[ name ]; 
                copy= options[ name ]; 
                //Prevent never-ending loop 
                if( target === copy ) { 
                   continue; 
                } 
                //Recurse if we're merging plain objects or arrays 
                if( deep && copy && ( jQuery.isPlainObject(copy) || (copyIsArray= jQuery.isArray(copy)) ) ) { 
                   if( copyIsArray ) { 
                       copyIsArray= false; 
                       clone= src && jQuery.isArray(src) ? src : []; 
                   }else { 
                       clone= src && jQuery.isPlainObject(src) ? src : {}; 
                   } 
                   //Never move original objects, clone them 
                   target[name ] = jQuery.extend( deep, clone, copy ); 
                //Don't bring in undefined values 
                }else if ( copy !== undefined ) { 
                   target[name ] = copy; 
                } 
            } 
        } 
    } 
    // Returnthe modified object 
    return target; 
}; 

var a={}; 
$.extend(a,{name:"hello"},{age:10}); 
console.log(a);//Object{name: "hello", age: 10} 

var a={}; 
varb={name:"hello"}; 
$.extend(a,b); 
console.log(a);//Object{name: "hello"} 
a.name="hi"; 
console.log(b);//Object{name: "hello"} 

var a={}; 
varb={name:{age:10}}; 
$.extend(a,b); 
console.log(a.name);//Object{age: 10} 
a.name.age=20; 
console.log(b.name);//Object{age: 20} 

var a={}; 
varb={name:{age:10}}; 
$.extend(true,a,b); 
console.log(a.name);//Object{age: 10} 
a.name.age=20; 
console.log(b.name);//Object{age: 10} 

 var a={name:{job:"Web Develop"}}; 
var b={name:{age:10}}; 
$.extend(true,a,b); 
console.log(a.name);//age: 10 job: "Web Develop" 

  //b.name没有覆盖a.name.job。