AngularJS extend用法详解及实例代码

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AngularJS extend用法

angular.extend:依次将第二个参数及后续的参数的第一层属性（不管是简单属性还是对象）拷贝赋给第一个参数的第一层属性，即如果是对象，则是引用的是同一个对象，并返回第一个参数对象。

实例一：var r = angular.extend(b, a);将对象a的第一层属性（不管是简单属性还是对象）拷贝赋给对象b的第一层属性，即如果是对象，则是引用的是同一个对象，并返回对象b

Js代码

var a = { 
  name : 'bijian', 
  address : 'shenzhen', 
  family : { 
    num : 6, 
    amount : '80W' 
  } 
}; 
var b = {}; 
var r = angular.extend(b, a); 
console.log('a:' + JSON.stringify(a)); 
console.log('b:' + JSON.stringify(b)); 
console.log('r:' + JSON.stringify(r)); 
 
b.address = 'hanzhou'; 
b.family.amount = '180W'; 
console.log('a:' + JSON.stringify(a)); 
console.log('b:' + JSON.stringify(b)); 
console.log('r:' + JSON.stringify(r));

运行结果：

Text代码

a:{"name":"bijian","address":"shenzhen","family":{"num":6,"amount":"80W"}} 
b:{"name":"bijian","address":"shenzhen","family":{"num":6,"amount":"80W"}} 
r:{"name":"bijian","address":"shenzhen","family":{"num":6,"amount":"80W"}} 
a:{"name":"bijian","address":"shenzhen","family":{"num":6,"amount":"180W"}} 
b:{"name":"bijian","address":"hanzhou","family":{"num":6,"amount":"180W"}} 
r:{"name":"bijian","address":"hanzhou","family":{"num":6,"amount":"180W"}}

实例二：var r = angular.extend(b, a, z);相继将对象a、z的第一层属性（不管是简单属性还是对象）拷贝赋给对象b的第一层属性，即如果是对象，则是引用的是同一个对象，并返回对象b

Js代码

var a = { 
  name : 'bijian', 
  address : 'shenzhen', 
  family : { 
    num : 6, 
    amount : '80W' 
  } 
}; 
var z = { 
  family : { 
    amount : '150W', 
    mainSource : '经营公司' 
  } 
}; 
var b = {}; 
var r = angular.extend(b, a, z); 
console.log('a:' + JSON.stringify(a)); 
console.log('b:' + JSON.stringify(b)); 
console.log('r:' + JSON.stringify(r)); 
 
b.address = 'hanzhou'; 
b.family.amount = '180W'; 
console.log('a:' + JSON.stringify(a)); 
console.log('b:' + JSON.stringify(b)); 
console.log('r:' + JSON.stringify(r));

运行结果：

Text代码

a:{"name":"bijian","address":"shenzhen","family":{"num":6,"amount":"80W"}} 
b:{"name":"bijian","address":"shenzhen","family":{"amount":"150W","mainSource":"经营公司"}} 
r:{"name":"bijian","address":"shenzhen","family":{"amount":"150W","mainSource":"经营公司"}} 
a:{"name":"bijian","address":"shenzhen","family":{"num":6,"amount":"80W"}} 
b:{"name":"bijian","address":"hanzhou","family":{"amount":"180W","mainSource":"经营公司"}} 
r:{"name":"bijian","address":"hanzhou","family":{"amount":"180W","mainSource":"经营公司"}}

再多的实例也不如源代码来的简单、直接和准确，angular.extend源码如下：

Js代码

/** 
 * @ngdoc function 
 * @name angular.extend 
 * @function 
 * 
 * @description 
 * Extends the destination object `dst` by copying all of the properties from the `src` object(s) 
 * to `dst`. You can specify multiple `src` objects. 
 * 
 * @param {Object} dst Destination object. 
 * @param {...Object} src Source object(s). 
 * @returns {Object} Reference to `dst`. 
 */ 
function extend(dst) { 
 var h = dst.$$hashKey; 
 forEach(arguments, function(obj){ 
  if (obj !== dst) { 
   forEach(obj, function(value, key){ 
    dst[key] = value; 
   }); 
  } 
 }); 
 
 setHashKey(dst,h); 
 return dst; 
}

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