-
Notifications
You must be signed in to change notification settings - Fork 27
/
defineProperty.html
154 lines (131 loc) · 2.96 KB
/
defineProperty.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<!-- <meta http-equiv="refresh" content="5"> -->
<title>Object.defineProperty</title>
<link rel="stylesheet" href="">
</head>
<body>
<!-- <div style="height: 1200px;">自动刷新页面</div> -->
<div class="app">{{ num }}</div>
<button class="btn">+</button>
<script>
/*
对象属性:数据属性、访问器属性
访问器属性由 “getter” 和 “setter” 方法表示。在对象字面量中,它们用 get 和 set 表示
从外表看,访问器属性看起来就像一个普通属性。这就是访问器属性的设计思想。我们不以函数的方式调用 user.getName,我们正常读取它:getter 在幕后运行
Object.defineProperty()
*/
let user = {
name: 'liben',
age: 28,
say () {
console.log('wuwuwu')
},
get getName () {
return 123;
},
set setAge (value) {
this.age = value
}
}
console.log(user.getName, user.name, user.age)
user.say()
user.setAge = 27
console.log(user.age)
console.log('--------------------')
let car = {};
Object.defineProperty(car, 'price', {
enumerable: true,
configurable: true,
get: function(value) {
console.log("读取属性值>>>>>", value);
return 300;
},
set: function (newVal, oldVal) {
oldVal = newVal
console.log("设置属性值>>>>>", newVal, oldVal);
}
})
car.price = 12;
console.log(car.price);
/*
实现一个Vue2的双向绑定
*/
function observe(obj) {
if (!obj || typeof obj !== 'object') {
return
}
Object.keys(obj).forEach(key => {
defineReactive(obj, key, obj[key])
})
}
function defineReactive(obj, key, val) {
// 递归子属性
observe(val);
let dep = new Dep();
Object.defineProperty(obj, key, {
enumerable: true,
configurable: true,
get: function() {
console.log('get value')
if (Dep.target) {
dep.addSub(Dep.target)
}
return val;
},
set: function(newVal) {
console.log('change value')
val = newVal;
dep.notify()
}
})
}
class Dep {
constructor() {
this.subs = []
}
addSub(sub) {
// sub是Watcher实例
this.subs.push(sub)
}
notify() {
this.subs.forEach(sub => {
sub.update()
})
}
}
// 全局属性,通过该属性配置 Watcher
Dep.target = null
function update(value) {
document.querySelector('.app').innerText = value
}
class Watcher {
constructor(obj, key, cb) {
Dep.target = this;
this.cb = cb;
this.obj = obj;
this.key = key;
this.value = obj[key];
Dep.target = null;
}
update() {
this.value = this.obj[this.key]
this.cb(this.value)
}
}
var data = {
num: "liben"
}
observe(data)
new Watcher(data, 'num', update)
let num = data.num;
data.num = 1;
document.querySelector(".btn").addEventListener("click", () => {
data.num ++
})
</script>
</body>
</html>