var obj = {
get a() {
return 2;
},
get c() {
return 34
}
}
Object.defineProperty(
obj,
'b',
{
get: function () {
return this.a * 2
},
enumerable: true
}
)
console.log(obj);
/*
* a: 2
* b: 4
* c: 34
* get a: ƒ a()
* get b: ƒ ()
* get c: ƒ c()
//有set就得有get 不然会出现去怪问题
var obj1 = {
get a() {
return this._a_;
},//有点像初始化变量
set a(val) {
this._a_ = val + 4;
}//类似于变量的赋值 如果没有set obj1.a为undefined 就算下面赋值也不行
};
obj1.a = 3;
console.log(obj1.a)
/*对象的属性操作符 是否可以枚举*/
var obj2 = {name:'hxq'};
Object.defineProperty(
obj2,
'a',
{
value:2,
enumerable:true
}
)
Object.defineProperty(
obj2,
'b',
{
value:3,
enumerable:false
}
)
console.log(obj2);
/*for in 遍历下标*/
for (let i in [1,1,1,3,232,3]){
console.log(i) //可以通过遍历下标来遍历值
}
// for of 直接遍历值
for (let i of [21312,,1,31,3,123,1]){
console.log(i)
}
/*for of 原理内置的@@iterator来手动遍历数组*/
var arr=[12,231,32,32];
var it=arr[Symbol.iterator]();
console.log(it)
console.log(it.next());//{value: 12, done: false}
console.log(it.next());//{value: 231, done: false}
console.log(it.next());//{value: 32, done: false}
console.log(it.next());//{value: 32, done: false}
console.log(it.next());//{value: undefin, done: true}