如何迭代JavaScript对象？ [英] How to iterate over a JavaScript object?

问题描述

我在JavaScript中有一个对象：

I have an object in JavaScript:

{
    abc: '...',
    bca: '...',
    zzz: '...',
    xxx: '...',
    ccc: '...',
    // ...
}

我想用代替循环以获取其属性。我希望在部分中迭代它（不是所有对象属性一次）。

I want to use a for loop to get its properties. And I want to iterate it in parts (not all object properties at once).

使用简单的数组我可以使用标准的来实现 loop：

With a simple array I can do it with a standard for loop:

for (i = 0; i < 100; i++) { ... } // first part
for (i = 100; i < 300; i++) { ... } // second
for (i = 300; i < arr.length; i++) { ... } // last

但如何用对象做？

推荐答案

对于大多数对象，在中使用 ...：

For most objects, use for .. in :

for (var key in yourobject) {
  console.log(key, yourobject[key]);
}

使用ES6，如果同时需要键和值，请执行

With ES6, if you need both keys and values simultaneously, do

for (let [key, value] of Object.entries(yourobject)) {
    console.log(key, value);
}

为避免记录继承的属性，请检查 hasOwnProperty ：

To avoid logging inherited properties, check with hasOwnProperty :

for (var key in yourobject) {
   if (yourobject.hasOwnProperty(key)) {
      console.log(key, yourobject[key]);
   }
}

此MDN文档更详细地解释了如何处理对象及其属性。

This MDN documentation explains more generally how to deal with objects and their properties.

如果你想以块为单位，最好是提取数组中的键。由于订单无法保证，这是正确的方法。在现代浏览器中，您可以使用

If you want to do it "in chunks", the best is to extract the keys in an array. As the order isn't guaranteed, this is the proper way. In modern browsers, you can use

var keys = Object.keys(yourobject);

为了更兼容，你最好这样做：

To be more compatible, you'd better do this :

 var keys = [];
 for (var key in yourobject) {      
     if (yourobject.hasOwnProperty(key)) keys.push(key);
 }

然后你可以按索引迭代你的房产： yourobject [keys [i]] ：

Then you can iterate on your properties by index: yourobject[keys[i]] :

for (var i=300; i<keys.length && i<600; i++) { 
   console.log(keys[i], yourobject[keys[i]]);
}

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