JavaScript-如何创建一个保证顺序的关联数组? [英] JavaScript - How to create an associative array that guarantees order?

问题描述

如何创建保证订单的关联数组?

对象(不保证订单):

var obj = {
  "first":"first",
  "2":"2",
  "34":"34",
  "1":"1",
  "second":"second"
};
for (var i in obj) {
    console.log(i);
};

结果:

1
2
34
first
second

数组:

var a = new Array();
a['first'] = "first";
a['2'] = "2";
a['34'] = "34";
a['1'] = "1";
a['second'] = "second";
console.log(a); // [1: "1", 2: "2", 34: "34", first: "first", second: "second"]

for (var i in a) {
    console.log(i);
};

结果:

1
2
34
first
second

该数组根本不能保证顺序.

The array does not guarantee order at all.

如何创建一个可以保证顺序的正确数组?

How can I create a correct array that guarantees order then?

推荐答案

在ECMAScript 6中，映射类型是键-值对的有序列表，其中键和值都可以具有任何类型. Map对象按插入顺序对其元素进行迭代.

In ECMAScript 6 Map type is an ordered list of key-value pairs, where both the key and the value can have any type. A Map object iterates its elements in insertion order.

forEach方法按插入顺序对Map对象中的每个键/值对执行一次提供的功能.

The forEach method executes a provided function once per each key/value pair in the Map object, in insertion order.

var a = new Map;
a.set("first", "first");
a.set("2", "2");
a.set("34", "34");
a.set("1", "1");
a.set("second", "second");

a.forEach(function(value, key) {
  console.log(key + ' => ' + value)
})

您还可以使用for...of循环，它会为每次迭代返回一个[key, value]数组.

You can also use for...of loop and it returns an array of [key, value] for each iteration.

var a = new Map;
a.set("first", "first");
a.set("2", "2");
a.set("34", "34");
a.set("1", "1");
a.set("second", "second");

for (var p of a) console.log(p)

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