map可以是 任意数据类型
let num = 123; let arr = [1, 2, 3, 4]; let fun = function () { }; let obj = {}; const map1 = new Map(); map1.set(num, "q1"); map1.set(arr, "q2"); map1.set(fun, "q3"); map1.set(obj, "q4"); map1.set('aaa', "q5"); for (const key of map1.keys()) { console.log(typeof (key)); // number object function object string }map的基本用法示例
const map2 = new Map([ ["s1", "as1"], ["s2", "as2"], ["s3", "as3"], ["s4", "as4"] ]) map2.set("s5", "as5") map2.delete("s3") console.log(map2.size); // 4 console.log(map2.get('s2')); // as2 console.log(map2.has("s3")); // false console.log(map2); // {"s1" => "as1", "s2" => "as2", "s4" => "as4", "s5" => "as5"} let arr1 = [...map2.values()] let arr2 = [...map2.keys()] let arr3 = [...map2.entries()] console.log(arr1); // 显示values值 ["as1", "as2", "as4", "as5"] console.log(arr2); // 显示key值 ["s1", "s2", "s4", "s5"] console.log(arr3); // 显示key值 [["s1", "as1"], ["s2", "as2"], ["s4", "as4"],["s5", "as5"]]