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// set:数组和对象的映射，或抽象
var s = new Set(["hello",7,"world",7,"world",7,"world"]);
console.log(s);//{"hello", 7, "world"} set不会重复
console.log(typeof s);//object
console.log(s[0]);//u
console.log(s[1]);//u
console.log(s[2]);//u
console.log(s.length);//u
for(var i of s){
console.log(i)//hello 7 world
}
var s = new Set();
s.add(3)
s.add(4)
s.add(5)
s.add("3")
console.log(s)//Set(4) {3, 4, 5, "3"}// Set集合是默认去重复的，但前提是两个添加的元素严格相等 所以3和"3"不相等，两个new出来的字符串不相等
for(var i of s.keys()){ //数组keys就是他本身
console.log(i) //3 4 5 3
}
for(var i of s.values()){
console.log(i) //3 4 5 3
}
for(var i of s.entries()){
console.log(i)//[3,3] [4,4] [5,5] [3,3]
}
// map 关于遍历的方法 由于Set集合本质上还是一个map，因此会有以下几种奇怪的遍历方法
var m = new Map();
m.set("name","admin");
m.set("age",18);
console.log(m);//Map(2) {"name" => "admin", "age" => 18} //不是箭头函数
console.log(typeof m);//object
console.log(m.get("name"));//admin
console.log(m.get("age"));//18
console.log(m.name); //undefined
console.log(m.age);//u
for(var i of m){
console.log(i) // ["name", "admin"] ["age", 18]
}
for(var i of m.keys()){
console.log(i) //name age
}
for(var i of m.values()){
console.log(i) //admin 18
}
for(var i of m.entries()){
console.log(i) //["name", "admin"] ["age", 18]
}
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