How to merge each object within arrays by index?

Question

How can I merge two arrays of objects of same length?

var array1 = [
  {name: \"lang\", value: \"English\"}, 
  {name: \"age\", value: \"18\"}
];
var array2 = [
         


        

Answer 1

A simple map with an Object.assign will do it. Assign unto a new empty object in order to avoid mutating the existing objects.

var array1 = [
  {name: "lang", value: "English"}, 
  {name: "age", value: "18"}
];
var array2 = [
  {code: "EN", text: "English language"}, 
  {code: "DE", value: "German", text: "German language"}
];

var array3 = array1.map((obj, index) => Object.assign({}, obj, array2[index]));

console.log(array3);

If you have an unknown number of arrays like this:

const arrays = [
  array1,
  array2,
  array3,
  // …
];

then you can use this approach:

const mergedArray = Array.from({
  length: arrays[0].length
}, (_, index) => Object.assign({}, ...arrays.map(({[index]: obj}) => obj))));

See this in action with the following example:

const arrays = [
  [
    {a: 3, b: 5},
    {a: 7, b: 2},
    {a: 1}
  ],
  [
    {b: 8, c: 42},
    {a: 1, b: 12, c: 44},
    {b: 0}
  ],
  [
    {d: 14, e: 15},
    {d: 7},
    {a: 10}
  ]
];

console.log(Array.from({
  length: arrays[0].length
}, (_, index) => Object.assign({}, ...arrays.map(({[index]: obj}) => obj))));