Javascript：检查对象是否没有属性，或者映射/关联数组是否为空 [英] Javascript: Checking if an object has no properties or if a map/associative-array is empty

问题描述

可能重复：

如何从JSON中测试一个空的Javascript对象？

在Javascript中有没有一个简单的方法来检查对象是否没有属性？或者换句话说，检查地图/关联数组是否为空的简单方法？例如，假设你有以下几点：

Is there an easy way to check if an object has no properties, in Javascript? Or in other words, an easy way to check if a map/associative array is empty? For example, let's say you had the following:

var nothingHere = {};
var somethingHere = {foo: "bar"};

有没有一个简单的方法来判断哪个是空？我唯一可以想到的是这样的：

Is there an easy way to tell which one is "empty"? The only thing I can think of is something like this:

function isEmpty(map) {
   var empty = true;

   for(var key in map) {
      empty = false;
      break;
   }

   return empty;
}

<

Is there a better way (like a native property/function or something)?

推荐答案

尝试这样：

function isEmpty(map) {
   for(var key in map) {
      return !map.hasOwnProperty(key);
   }
   return true;
}

您的解决方案也可以，但只有当没有库扩展 Object 原型。它可能或可能不够好。

Your solution works, too, but only if there is no library extending the Object prototype. It may or may not be good enough.

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