How to Convert a nested array to an object

Question

I want to create an object from a nested array only 2 levels deep. The function I came up with returns

[{ key1: 'value1', key2: 'value2' }]

rather than

[{ key1: 'value1' }, {key2: 'value2' }]

I've also tried replacing the if statement with obj[elem[0]] = elem[1]; but get the same result.

How can I create separate objects for each nested array?

var array = [["key1", "value1"], ["key2", "value2"]]

function nestedArrToObj(array){

  let obj = {};

  for (let i=0; i < array.length;i++) {
    let elem = array[i];

    if (!(obj[elem[0]])) {
      obj[elem[0]] = elem[1]
    }
  }

  return [obj];
}

Ele · Accepted Answer · 2018-03-03 03:54:50Z

2

Using the function map

let array = [["key1", "value1"], ["key2", "value2"]];
let result = array.map(([key, value]) => ({[key]: value}));

console.log(result)

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Using the function reduce

let array = [["key1", "value1"], ["key2", "value2"]];
let result = array.reduce((a, c) => {
  let [key, value] = c;
  return [...a, {[key]: value}];
}, []);

console.log(result)

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Cross-browser and backend technology compatible approach:

var array = [["key1", "value1"], ["key2", "value2"]];

var result = [];
for(var a of array) {
  var value = a.pop();
  var key = a.pop();
  
  var object = {};
  object[key] = value;
  
  result.push(object);
}

console.log(result)

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edited Mar 3, 2018 at 3:54

answered Mar 3, 2018 at 3:33

Ele

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5 Comments

e1v1s Over a year ago

I appreciate the response but I was trying to get each nested array as a separate object

e1v1s Over a year ago

So for the answer using reduce in this line - let [key, value] = c; - you can "unpack" the array in c as separate array objects? like I could use c[0] in place of key in your answer?

Ele Over a year ago

@e1v1s that's called Destructuring assignment, basically get the index 0 and 1 and assign those values to key and value - Destructuring assignment

georg Over a year ago

Actually, map is more appropriate here than reduce, because it's an N->N and not N->1 transform.

Ele Over a year ago

@georg you're right, I updated the answer. It's really straightforward with function map.

גלעד ברקן · Accepted Answer · 2018-03-03 03:42:38Z

1

Here's a version with map:

console.log(
  [["key1", "value1"], ["key2", "value2"]]
      .map(x => {let obj = {}; obj[x[0]] = x[1]; return obj;})
)

answered Mar 3, 2018 at 3:42

גלעד ברקן

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2 Comments

georg Over a year ago

Yep, .map is correct here, In ES6: a.map(([k, v]) => ({[k]: v}))

גלעד ברקן Over a year ago

@georg thanks! I was looking for how to assign the key like that, lol

jens · Accepted Answer · 2018-03-03 03:37:58Z

0

Some of the newer features of the language make this a bit easier. This is an ES5 solution.

var array = [["key1", "value1"], ["key2", "value2"]]

function nestedArrToObj(array){
  return array.reduce(function(previous, current) {
      let obj = {};
      obj[current[0]] = current[1];
      previous.push(obj);
      return previous;
  }, []);
}

console.log(nestedArrToObj(array))

answered Mar 3, 2018 at 3:37

jens

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