angular.extend用法实例

        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

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：

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

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：

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：

/**
 * @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;
}