用一个或多个其他对象来扩展一个对象，返回这个被扩展的对象。这是简化继承的主要工具。

返回值:Object

参数:

• target (Object): 要扩展的对象
• prop1 (Object): 要与第一个对象合并的对象
• propN (Object): (可选) 更多要与第一个对象合并的对象

合并settings和options, 修改并返回settings

var settings = { validate: false, limit: 5, name: "foo"   };
var options = { validate: true, name: "bar" };
jQuery.extend(settings,   options); 

结果:

settings == { validate: true, limit: 5, name: "bar" }

合并defaults和options, 但不修改defaults，返回合并后的对象

ar defaults = { validate: false, limit: 5, name: "foo"   };
var options = { validate: true, name: "bar" };
var settings =   jQuery.extend({}, defaults, options); 

结果:

settings == { validate: true, limit: 5, name: "bar" }

Extend one object with one or more others, returning the original, modified, object. This is a great utility for simple inheritance.

Return value: Object
Parameters:

• target (Object): The object to extend
• prop1 (Object): The object that will be merged into the first.
• propN (Object): (optional) More objects to merge into the first

Example:

Merge settings and options, modifying settings

var settings = { validate: false, limit: 5, name: "foo" };   
var options = { validate: true, name: "bar" };   
jQuery.extend(settings, options);  

 settings == { validate: true, limit: 5, name: "bar" }  

Example:

Merge defaults and options, without modifying the defaults

 var empty = {};
 var defaults = { validate: false, limit: 5, name: "foo" };
 var options = { validate: true, name: "bar" };
 var settings = jQuery.extend(empty, defaults, options);  

 settings == { validate: true, limit: 5, name: "bar" }
 empty == { validate: true, limit: 5, name: "bar" }