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);//这里其实不关 a.family什么事，因为被后续的z给覆盖了
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';//这里改变不了a.family
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;
}