在JavaScript对象，什么是得到一个值的属性最好的方法？

问题描述：

如果我们有一个JavaScript对象

if we have a javascript object

var calories = { apple:200, pear:280, banana:300, peach:325 }

什么是找到（第一）的水果，有280卡路里的最佳方式？

what is best way to find the (first) fruit that has 280 calories?

能 Object.getOwnPropertyNames（卡路里）.forEach ... 但应该有一个更好的办法。

could Object.getOwnPropertyNames(calories).forEach... but there should be a better way.

例如，我在想 Array.prototype.indexOf的（）由它来完成同样的事情的Array。

For example, I was thinking of Array.prototype.indexOf() which does the same thing for an Array.

答

使用线性搜索的for..in 结构：

var fruit = null;

for (var prop in calories) {

  if (calories[prop] == 280) {

    fruit = prop;
    break;
  }
}