javascript - 按顺序获取 JSON 键

Question

我在文件中有以下内容并阅读为

var input = require("./mydata.json");

"User": {
        "properties": {
        "firstName": {
          "type": "string",
          "minLength": 1,
          "maxLength": 50
        },
        "lastName": {
          "type": "string",
          "maxLength": 50
        },
        "middleName": {
          "type": "string"
        },
        "title": {
          "type": "string"
        },
        "language": {
          "type": "string",
          "default": "en-US"
        }
      }
    }

我正在使用下面的代码来遍历键

var item = _.get(input, 'User');
var properties = item.properties;
var allKeys = _.keys(properties);
_.each(allKeys, function(key) {

});

在每个循环中，我按照与输入文件中相同的顺序获取名字、姓氏等。我想知道我是否总能把它整理好？

Answer 1

JavaScript 不保证对象中的属性顺序；您需要使用 Array 来保存它。

对象的定义来自 ECMAScript Third Edition (pdf) :

4.3.3 Object

An object is a member of the type Object. It is an unordered collection of properties each of which contains a primitive value, object, or function. A function stored in a property of an object is called a method.

自 ECMAScript 2015，使用 the Map object可能是另一种选择。 Map 与 Object 和 guarantees the keys order 有一些相似之处。 :

A Map iterates its elements in insertion order, whereas iteration order is not specified for Objects.