From 21b8e82a7fa2ab7f4f388fd7dc05e19fd54d58b3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=BD=97=E6=AD=A4=E4=B8=9C?= <3352403143@qq.com>
Date: Fri, 28 Oct 2022 10:48:51 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BD=9C=E4=B8=9A?=
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+ Document
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+### map&set
+
+###### map
+
+1.Map:键值对，类似于对象
+
+ 键是唯一的
+
+2.
+
+/创建map对象
+ //var map = new Map();
+
+
+ //添加
+ //map.set(1,'呼呼');
+ //map.set(2,"拉拉");
+ //console.log(map);
+
+ //查看 v
+ //console.log(map.get(1));
+
+ //删除
+ //map.delete(1);
+ //console.log(map);
+
+ //返回map存在的键的数组
+ //console.log(map.keys());
+
+ //返回map存在的值的数组
+ //console.log(map.values());
+
+ //返回map中存在的键值对的数组
+ //console.log(map.entries());
+
+ //查看键是否存在
+ //console.log(map.has(1));
+
+ //查看map的长度
+ //console.log(map.size);
+
+特殊情况：
+
+```
+// console.log(+0===-0); //true
+// console.log(Object.is(+0,-0)); //false
+// console.log(Object.is(+0,0));
+
+
+// let map = new Map();
+
+// map.set(-0, 123); //不管是+0,0,-0,当成了同一个键，
+// map.get(+0);
+
+```
+
+ //map转数组 []
+
+```
+//const arr = [...map]
+// const arr = []
+// for(let e of map.entries()){
+// arr.push(e)
+// }
+
+
+
+
+
+//数组转map
+// const arr = [['name', 'zoe'], ['age', 18]]
+// var map = new Map([
+// ['name', 'zoe'], ['age', 18]
+// ])
+```
+
+###### set
+
+对象类似于数组，且成员的值都是唯一的
+
+去重
+
+
+```
+ // const arr = [1,3,3,5,7,9];
+ // const arr2 = [...new Set(arr)];
+ // console.log(arr2);
+```
+
+
+
+ //Map 和 Set 都不允许键重复
+ //Set 不能通过迭代器来改变Set的值，因为Set的值就是键
+
+set 转数组
+
+```
+const arr = [...set]
+```
+
+数组转set:数组去重
+
+```
+const arrs = [1,3,54,5,6,5,5,5,5,5,5,5]
+ console.log(arrs.length);
+
+ var sets = new Set(arrs);
+```
+
+3.WeakSet
+
+WeakMap:弱引用(直接回收)，强引用(不会强制回收)
+
+```
+// var weakset = new WeakSet()
+
+ // var name = 'Joe'
+ // var map = new Map();
+ // map.set(name,'Zoe')
+
+ // var weakmap = new WeakMap();
+ // weakmap.set(name,'Zoe')
+```
+
--
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