继承模式
发展史
function inherit(Target,Origin){
Target.prototype = Origin.protortype;
//这种方式代表Target的原型指向Origin的原型,一旦改动Target的原型,Origin的原型也会发生改变
}
- 圣杯模式⭐
创建中间层
//圣杯模式
function inherit(Target,Origin){
function B(){};
B.prototype = Origin.protortype;
Target.protortype = new B();
//∵c.__proto__ ——> new B().__proto__ ——> Aa.prototype
//要使c.__proto__指向自身,↓
Target.protortype.constructor = Target;
Target.protortype.uper = Origin.protortype;//真正继承自
}
function Aa(){}
function C(){}
C.prototype.ch = "L";
inherit(C,Aa);
var a = new Aa;
var c = new C;
//input: c.ch //output: "L"
//input: a.ch //output: undefined
- yahoo提供的写法,利用闭包将属性封装为私有
var inherit = (function(){
var B = function(){};
return function(Targrt,Origin){
B.prototype = Origin.protortype;
Target.protortype = new B();
Target.protortype.constructor = Target;
Target.protortype.uper = Origin.protortype;
}
}())//形成闭包
命名空间
- 管理变量,防止污染全局,适用于模块化开发(闭包)
var name = 'bcd';
var init = (function(){
var name = 'abc';
function callName(){
console.log(name);
}
return function(){
callName();
}
}())
init();
//在一个函数中return this指返回自己,可实现连续调用
var gidle = {
shua : function(){
console.log('叶舒华');
return this;
},
yuqi : function(){
console.log('宋雨琦');
return this;
}
}
gidle.shua().yuqi();
var Gidle = {
gidle1:{name: 'shua'},gidle2:{name: 'yuqi'},
gidle3:{name: 'mian'},gidle4:{name: 'Minnie'},
gidle5:{name: 'juan'},gidle6:{name: 'susu'},
Neverland: function(num){
return this['gidle' + num];
}//属性拼接
}
对象枚举
var obj = {
name: '1',
age : 18,
sex : 'female',
height: 175,
weight: 60
}
for(var prop in obj){
if(obj.hasOwnProperty(prop)){
console.log(obj[prop] );//枚举属性值
}
}
- for in
- hasOwnProperty
for(var prop in Origin){
if(Origin.hasOwnProperty(prop)){//为了避免拿原型链上的属性
}
}
- in
判断对象上能不能访问到该属性
'name' in obj ——>true
name in obj ——>报错: name为变量名而非属性
- instanceof
A instanceof B
判断A对象是不是B构造函数构造出来的
function Person(){}
var person = new Person();
this
- 函数预编译过程 this ——> window
- 全局作用域 this ——> window
- call/apply可以改变函数运行时this的指向
- obj.func(); func()里的this指向obj
判断数组/对象
- instanceof Object
- prototype
- Object.prototype.toString.call √