如何将项目推送和分组到数组

Question

I have searched many sites to find the answer to this question, I do not know exactly how to describe it, so, excuse me. I have a .json file with this structure:

"ntest": [
    {
        "dane": [
            {
                "label": "Product A",
                "mydane": [
                    {
                        "a": 20,
                        "y": "2018"
                    },
                    {
                        "a": 15,
                        "y": "2019"
                    },
                    {
                        "a": 35,
                        "y": "2020"
                    }
                ]
            },
            {
                "label": "Product B",
                "mydane": [
                    {
                        "a": 10,
                        "y": "2018"
                    },
                    {
                        "a": 15,
                        "y": "2019"
                    },
                    {
                        "a": 28,
                        "y": "2020"
                    }
                ]
            }
        ]

and what I want is to receive something like this:

apart I want to have only one value of each year. I have already reached this point but I cannot access the data, and the result is as follow.

And this is my method.

getNewData(): void {
const ay: string[] = ['2018', '2019', '2020'];
const year = new Array();
this.getndata().subscribe((ko: any[]) => {
  ko.forEach((lp) => {
    lp.dane.forEach((el: { label: any; mydane: MyDane[]; }) => {
      console.log(el.label);
      console.log(el.mydane);
      for (const ite of el.mydane) {
        year.push(ite.y);
      }
    });
  });
});
console.log(JSON.stringify(ay));
console.log(JSON.stringify(year));

// this.barChartLabels = yearray;

}

How can I get the result as in the first image? This is sringifi result

Answer 1

You can use a dictionary, also you can remove duplicates from the array, as Kelvin's said, then sorting them (dictionaries do that auto)

 let data = { "ntest": [ { "dane": [ { "label": "Product A", "mydane": [ { "a": 20, "y": "2018" }, { "a": 15, "y": "2019" }, { "a": 35, "y": "2020" } ] }, { "label": "Product B", "mydane": [ { "a": 10, "y": "2018" }, { "a": 15, "y": "2019" }, { "a": 28, "y": "2020" } ] } ] } ] } let yearsDict = {} data.ntest[0].dane.forEach((dane) => { dane.mydane.forEach((obj) => { yearsDict[obj.y] = obj.a }) }) console.log(Object.getOwnPropertyNames(yearsDict))

Answer 2

For your problem, there are two easy solutions I can think of:

• Instead of getting all the y 's from every dane , only get them for the first one. That's assuming that the structure will be the same for all the dane s
• Keep the result you have, but deduplicate the results. In other words, remove duplicates entries from the array

The latter can be easily done by storing your results in a Set instead of an array, which you can later convert to an array with Array.from(set) . Sets don't store duplicates because of their nature.