jQuery中extend()实现原理

jQuery.extend使用的几种方式

1.jQuery.extend(源对象)

jQuery源代码：

if(length == i){
     target = this;
     --i;  
}

示例1：

var person = {  
    sex      : 'male',  
    showName : function(name){  
            alert("Name: " + name);  
    }  
};  
jQuery.extend(person); // 将person对象扩展到jQuery（$）对象上  
jQuery.showName("admin"); // Name: admin  
$.showName("admin"); // Name: amdin  
alert("Sex: " + $.sex); // Sex: male

2.jQuery.extend(目标对象,源对象)

var person = {  
    language : ['java', 'c++', 'sql'],  
    showName : function(name){  
        alert("Name: " + name);  
    }  
};  
var student = {  
    showNum : function(num){  
        alert("Num: " + num);  
    }  
};  
jQuery.extend(student, person); // 将person对象扩展到指定的student对象上  
student.showName("admin");  
alert(student.language);

3.jQuery.extend(boolean,源对象)

var person = {  
    language : ['java', 'c++', 'sql'],  
    showName : function(name){  
        alert("Name: " + name);  
    }  
};  
jQuery.extend(true, person); // 将person对象扩展jQuery对象上  
alert($.language); // java, c++, sql  
$.language.push('PL/SQL'); // 修改扩展后的对象  
alert(person.language); // java, c++, sql  
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)

var person = {  
    showName : function(name){  
        alert("Name: " + name);  
    }  
};  
var student = {  
    language : ["java", "c++", "javascript"],  
    showNum : function(num){  
        alert("Num: " + num);  
    }  
};  
var target = jQuery.extend(person, student);  
alert(target.language);     // java, c++, javascript  
target.language.push("PL/SQL");  
alert(student.language);    // java, c++, javascript, PL/SQL  
student.language.pop();  
alert(target.language);     // java, c++, javascript  
var target2 = jQuery.extend(true, person, student);  
alert(target2.language);    // java, c++, javascript  
target2.language.push("PL/SQL");  
alert(student.language);    // java, c++, javascript  
student.language.pop();  
alert(target2.language);    // java, c++, javascript, PL/SQL

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