根据Javascript中的日期计算数组中的对象数量

Question

I have a reportsList include 1000 object report like this:

    {
        "id": 39,
        "userId": 3,
        "emotion": {
            "id": "worried",
            "name": "Worried Face",
            "colons": ":worried:",
            "emoticons": [],
            "native": "😟",
            "skin": null,
            "unified": "1f61f"
        },
        "title": "Enim consequatur in quia voluptatum.",
        "date": "2018-07-14",
        "achievement": "Necessitatibus libero voluptas quod autem voluptatum cupiditate hic.",
        "plan": "Suscipit molestiae rerum. Nostrum est est quae. Facere amet doloresam.",
        "issues": [
            "Keeping up with Technology"
        ],
        "description": "Qam iure earum iusto sapiente amet quaerat. Sed ducimus dolor et minus quas qui repudiandae.",
        "comment": "Quientore sed aliquid aut dolorum."
    }

Now I want to calculate number of emotion based on 4 months: 6, 7, 8, 9 and then count them.

This is my result that I'm expecting:

emotions = [20, 30, 40, 50]

How can we implement this one? Please give me some idea. Thanks!

Answer 1

You can try:

// untested

// desired months
const months = [6, 7, 8, 9];
// For each of the desired month
const emotions = months.map(month => {
  // Filter out the same month object
  const array = reportsList.filter(obj => {
    // Get the month per data
    const objMonth = new Date(obj.date).getMonth() + 1;
    // return true if it is the same month
    return month === objMonth;
  });
  // return the array length
  return array.length;
});

Answer 2

Something like this I guess:

const emoticonsByMonth = reportsList.reduce((acc, report) => {
    const month = new Date(report.date).getMonth();
    if (month >= 6 && month <= 9) acc[month - 5] += 1;
    return acc;   
}, [0, 0, 0, 0]);

getMonth() return the month starting from 0 so Jun would be 5 ... that's why you have to increment at month - 5 and not month - 6