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javascriptarraysjavascript-objects

Efficient way to convert Object arrays into collection in Javascript

const myObj = {
 a: [1, 2, 3],
 b: [2, 4, 6],
 c: [10, 20, 30]
}

Into

const myCollection = [
  {a: 1, b: 2, c: 10},
  {a: 2, b: 4, c: 20},
  {a: 3, b: 6, c: 30}
]

I tried combinations of Object.entries, Object.keys and map but I'm always finding myself iterating twice or more over myObj and I'm not happy with any solution I came up with. So what is the most efficient (in terms of time complexity) and elegant way that you can think to achieve that?

Solution

  • You could reduce the entries and map nested arrays.

    const
    object = { a: [1, 2, 3], b: [2, 4, 6], c: [10, 20, 30] },
    result = Object
        .entries(object)
        .reduce((r, [k, a]) => a.map((v, i) => ({ ...r[i], [k]: v })), []);

console.log(result);