JavaSript-Map

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示例一：Map()

var map = new Map();map.set(1, 1);map.set(2, 4);map.set(3, 9);console.log("3: " + map.has(3)); // 3: trueconsole.log("3: " + map.get(3)); // 3: 9console.log("4: " + map.has(4)); // 4: falsemap.delete(3);console.log("3: " + map.get(3)); // 3: undefined

示例二：array-like

var students = {}; // Cannot be undefined.function init() {  for (var i = 0; i < 5; i++) {    students[i + 1] = {      name : "name" + i,      city : "city" + i    }  }}function print() {  var id = 0;  for (var id in students) {    console.log(id + ": [name=" + students[id].name + ",city=" + students[id].city + "]");  }}function printSingle(id) {  if (id in students) {    console.log("Found. " + id + ": [name=" + students[id].name + ",city=" + students[id].city + "]");  } else {    console.log("Not found " + id + ".");  }}init();/*1: [name=name0,city=city0]2: [name=name1,city=city1]3: [name=name2,city=city2]4: [name=name3,city=city3]5: [name=name4,city=city4]*/print();//Found. 3: [name=name2,city=city2]printSingle(3);//Not found 30.printSingle(30);delete students[3];/*1: [name=name0,city=city0]2: [name=name1,city=city1]4: [name=name3,city=city3]5: [name=name4,city=city4]*/print();//length: undefinedconsole.log("length: " + students.length);

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