javascript - 获取_.groupBy的值

Question

我的 JavaScript 有问题。代码如下:

var myDB = [
    { xCounter: 'positive', day: 'first' }, 
    { xCounter: 'positive', day: 'second' }
];

var days = _.groupBy(myDB, 'day');

如何获得“天”的第一个、第二个、第三个...值？

谢谢!

Answer 1

根据您给出的示例:

var myDB =  [{ "xCounter": "positive", "day": "first" }, { "xCounter": "positive", "day": "second" }];

使用 groupBy 方法，您将在 days 变量中获得以下结果:

{
  first: [{ "xCounter": "positive", "day": "first" }],
  second: [{ "xCounter": "positive", "day": "second" }]
}

要查看此结果，您可以使用以下代码片段:

for (var day in days) {
  if (days.hasOwnProperty(day)) {
    // do something with 'day' (which will take tha values 'first' and 'second')
    // and 'days[day]' (which is an array of {xCounter: X, day: Y} objects)
  }
}

PS:如果可能的话，我建议使用 Lodash 而不是 Underscore ( https://lodash.com/docs/4.16.1#groupBy )，因为 Lodash 开发更加活跃，但这是我的观点;)