How to group array element to a new group array?-CodePudding

I have an array of lines:

   this.lines = [
    0: {indexLine: 0, group: 16, columns: [,…]}
    1: {indexLine: 1, group: 16,…}
    2: {indexLine: 2, group: 16,…}
    3: {indexLine: 3, group: 9,…}
    ]

I want to group lines by group to be able render it in different tables.

I have tried this:

 let arr: any = {};
        this.lines.forEach((line) => {
          if (!arr[line.group]) {
            arr[line.group] = [];
          }

          arr[line.group].push(line);
        });

CodePudding user response：

You can use Set to get unique group values from array of object. new Set(lines.map(x => x.group) will give you array of unique values of group.

Convert that set to array with Array.from().

Now you can use map to iterate through unique group values and Array.filter would give you all matching elements.

let lines = [
    {indexLine: 0, group: 16},
    {indexLine: 1, group: 16},
    {indexLine: 2, group: 16},
    {indexLine: 3, group: 9},
];

const groupedLines = Array.from(new Set(lines.map(x=>x.group))).map(y => lines.filter(z => z.group === y));

console.log(groupedLines);

CodePudding user response：

You could use the reduce method to get what you want:

const result = this.lines.reduce((acc, item) => {
  if (!acc[item.group]) {
    acc[item.group] = [];
  }
  acc[item.group].push(item);
  return acc;
}, {});

If you want to get all the groups as multiple arrays instead of an object, you can use Object.values to do just that:

const groups = Object.values(result);

CodePudding user response：

you can use lodash.groupBy

yarn add lodash.groupby ( or npm install lodash.groupby --save )

import groupBy from 'lodash.groupby'; // 12.6k (gzipped 4.8k)

// ...

console.log(groupBy(this.lines, ({group}) => group)));

( self-explanatory code there, 0 WTFs per minute )