How to split nested Object into Array of Objects - avoiding for loop

Question

I want to split a nested Object into an Array of Objects. I am able to achieve the same using two FOR Loops.

Is there any way I can have a better solution, or this is correct?

Below snippet for reference.

 var Input = {
      "English": {
        "v1": "10",
        "v2": "11",
        "v3": "34"
      },
      "Hindi": {
        "v1": "14",
        "v2": "16",
        "v3": "18"
      }
    }
    var Output = []

 for (let i = 0; i < Object.keys(Input).length; i++) {
      for (let j = 0; j<Object.keys(Object.values(Input)[i]).length; j++) {
        Output.push({
          "parameter": Object.keys(Input)[i],
          "machine": Object.keys(Object.values(Input)[i])[j],
          "value":Object.values(Object.values(Input)[i])[j]
        })
      }
    }


console.log(Output)

There is nothing wrong with your solution. There will be varying opinions about how to go about the task you defined. Your question title says "avoiding for loop" - why? The for loop is the fastest iterator available in JavaScript, is well understood, and is reliable. You have not stated a reason for "avoiding for loop". There are some, but if you would like to elaborate please do. — Randy Casburn
– Randy Casburn, Commented Jan 24, 2021 at 20:01
As a side note, you should consider caching data that does not change. You call Object.keys(Input) repeatedly - call it once and cache the results for reuse. — Randy Casburn
– Randy Casburn, Commented Jan 24, 2021 at 20:03
Take a look at for (const [key, value] of Object.entries(Input)) {...}. — Teemu
– Teemu, Commented Jan 24, 2021 at 20:14
@RandyCasburn Thanks for your comment, yeah for loop is definitely reliable but can't say it as the fastest. Object.entries() and Array.flatMap() looks relevant for large size records. — Gunjan Anshul
– Gunjan Anshul, Commented Jan 25, 2021 at 14:50

cbr · Accepted Answer · 2021-01-24 20:17:49Z

3

You could use Object.entries() and Array.flatMap():

var Input = {
  English: {
    v1: "10",
    v2: "11",
    v3: "34",
  },
  Hindi: {
    v1: "14",
    v2: "16",
    v3: "18",
  },
};

const Output = Object.entries(Input).flatMap(([parameter, values]) =>
  Object.entries(values).map(([machine, value]) => ({
    parameter,
    machine,
    value,
  }))
);

console.log(Output);

Here the .flatMap() flattens the arrays created by the Object.entries().map() into one big array. It also uses array destructuring to pick out the key and value from the tuple which Object.entries() produces.

answered Jan 24, 2021 at 20:17

cbr

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