## Map * new Map() * has * get * delete * clear * size ### 初始化 Map ``` new Map([["name", "coco"], ["age", 18]]) // Map(2) {"name" => "coco", "age" => 18} ``` ``` new Map({ [Symbol.iterator]: function *() { yield ["name", "coco"] yield ["age", 18] } }) // Map(2) {"name" => "coco", "age" => 18} ``` ### 和 Object 的对比 | Map | Object | | --- | --- | | Map 可以保证顺序 | 不可以 | | Map 的 delete 性能好 | | | 存储的键值对更多 | | | | 数据量少时，object查找更快 | | 大量的插入操作，Map更适合 | | ## WeakMap https://www.jianshu.com/p/8c4ffa77b346 ## Set * new Set() * has * add * delete * clear * size * 维护顺序 ### 初始化 Set ``` new Set(["name", "coco"]) // Set(2) {"name", "coco"} ``` ``` new Set({ [Symbol.iterator]: function *() { yield "name" yield "age" } }) // Set(2) {"name", "age"} ``` ## WeakSet