jQuery中extend()实现原理

jQuery.extend使用的几种方式

1.jQuery.extend(源对象)

 1 jQuery源代码：
 2 
 3 if(length == i){
 4      target = this;
 5      --i;  
 6 }
 7 
 8 示例1：
 9 
10 var person = {  
11     sex      : 'male',  
12     showName : function(name){  
13             alert("Name: " + name);  
14     }  
15 };  
16 jQuery.extend(person); // 将person对象扩展到jQuery（$）对象上  
17 jQuery.showName("admin"); // Name: admin  
18 $.showName("admin"); // Name: amdin  
19 alert("Sex: " + $.sex); // Sex: male

2.jQuery.extend(目标对象,源对象)

 1 var person = {  
 2     language : ['java', 'c++', 'sql'],  
 3     showName : function(name){  
 4         alert("Name: " + name);  
 5     }  
 6 };  
 7 var student = {  
 8     showNum : function(num){  
 9         alert("Num: " + num);  
10     }  
11 };  
12 jQuery.extend(student, person); // 将person对象扩展到指定的student对象上  
13 student.showName("admin");  
14 alert(student.language);

3.jQuery.extend(boolean,源对象)

 1 var person = {  
 2     language : ['java', 'c++', 'sql'],  
 3     showName : function(name){  
 4         alert("Name: " + name);  
 5     }  
 6 };  
 7 jQuery.extend(true, person); // 将person对象扩展jQuery对象上  
 8 alert($.language); // java, c++, sql  
 9 $.language.push('PL/SQL'); // 修改扩展后的对象  
10 alert(person.language); // java, c++, sql  
11 person.language.pop();

从上面例子中可以看出对$.language的修改不会影响到person中的language属性。这就是深度复制

4.jQuery.extend(boolean,目标对象,源对象)

 1 var person = {  
 2     showName : function(name){  
 3         alert("Name: " + name);  
 4     }  
 5 };  
 6 var student = {  
 7     language : ["java", "c++", "javascript"],  
 8     showNum : function(num){  
 9         alert("Num: " + num);  
10     }  
11 };  
12 var target = jQuery.extend(person, student);  
13 alert(target.language);     // java, c++, javascript  
14 target.language.push("PL/SQL");  
15 alert(student.language);    // java, c++, javascript, PL/SQL  
16 student.language.pop();  
17 alert(target.language);     // java, c++, javascript  
18 var target2 = jQuery.extend(true, person, student);  
19 alert(target2.language);    // java, c++, javascript  
20 target2.language.push("PL/SQL");  
21 alert(student.language);    // java, c++, javascript  
22 student.language.pop();  
23 alert(target2.language);    // java, c++, javascript, PL/SQL

转载自http://www.jb51.net/article/61478.htm