Map objects hold key-value pairs. Any value (object or raw value) can be a key or a value one. Key can be a string. Key can be an object. Key can be a function. Key can be NaN 2. An iteration in a Map traverses the Map with the following two superlatives. 1.for… of

var obj = {
            name: "Chu Wanning".age: 32.action: function() {
                console.log("Ink burning")}}for(var key in obj) {
            console.log(obj[key])
            / / chu rather late
            / / 32
            / / ƒ () {
            // console.log(" ink burning ")
            / /}
           // }
Copy the code

2.forEach()

var myMap = new Map(a);The set() method adds or updates a (new) key-value pair to the Map object with a specified key and value.
        myMap.set(0."zero");
        myMap.set(1."one");

        // Two logs will be displayed. One is "0 = zero" and one is "1 = one"
        myMap.forEach(function (value, key) {
            console.log(key + "=" + value);
            // 0 = zero
            // 1 = one
        }, myMap)
Copy the code

Operations on Map objects 1.Map and Array conversion

 var kvArray = [
            ["key1"."value1"],
            ["key2"."value2"]].var myMap = new Map(kvArray);
        console.log(myMap);
        The Map constructor converts a two-dimensional array of key-value pairs into a Map object
        var outArray = Array.from(myMap);
        console.log(outArray);
         The array. from function converts a Map object into a two-dimensional Array of key-value pairs
Copy the code

2. The Map of cloning

var myMap1 = new Map([["key1"."value1"],
            ["key2"."value2"]]);var myMap2 = new Map(myMap1);

        console.log(original === clone);
        // Print false. The Map object constructor generates instances and iterates out new objects.
Copy the code

3. The consolidation of the Map

var first = new Map([[1.'one'],
            [2.'two'],
            [3.'three']]);var second = new Map([[1.'uno'],
            [2.'dos']]);Uno, DOS, three; // If two maps have duplicate keys, the last one overwrites the previous one
        var merged = new Map([...first, ...second]);
Copy the code