How can I flatten 2D array in typescript?

Question

If I have an array in the following format:

[0]:
    ["id_1"]:
        prop1: "abc"
        prop2: "def" 
    ["id_2"]:
        prop1: "ghi"
        prop2: "jkl"
[1]:
    ["id_3"]:
        prop1: "mno"
        prop2: "pqr" 
    ["id_4"]:
        prop1: "stu"
        prop2: "vwx"

How could I map that into an array using the following format:

[0]:
    key: "id_1"
    prop1: "abc"
    prop2: "def" 
[1]:
    key: "id_2"
    prop1: "ghi"
    prop2: "jkl"
[2]:
    key: "id_3"
    prop1: "mno"
    prop2: "pqr" 
[4]:
    key: "id_4"
    prop1: "stu"
    prop2: "vwx"

I've tried using flatten functions as described here: Merge/flatten an array of arrays in JavaScript? but i'm not sure how i'd set the key for each flattened child element.

For what you are doing, you are not really simply flattening an array, but creating a brand new array from a mixture of arrays and properties. — Tim B James, Sep 26 '17 at 08:52

score 1 · Accepted Answer · answered Sep 26 '17 at 09:06

I'm not sure if the data structure is correct as you refuse to post it, but if I'm guessing right you can get the desired result with a reduce, map combination

let arr = [
    [{id_1: {prop1: 'abc', prop2: 'def'}}, {id_2: {prop1: 'ghi', prop2: 'jkl'}}],
    [{id_3: {prop1: 'abc', prop2: 'def'}}, {id_4: {prop1: 'ghi', prop2: 'jkl'}}]
];


function flatten(arr) {
  return arr.reduce((a, b) => {
    return a.concat(b.map(e => {
      let key = Object.keys(e)[0];
      return Object.assign({
        key
      }, e[key]);
    }))
  }, [])
}

console.log(flatten(arr));

How can I flatten 2D array in typescript?

1 Answers1