How to merge two object arrays of different size by key in JavaScript

Suppose, we have an object like this −

const obj = {    "part1": [{"id": 1, "a": 50},{"id": 2, "a": 55},{"id": 4, "a": 100}],    "part2":[{"id": 1, "b": 40}, {"id": 3, "b": 45}, {"id": 4, "b": 110}] };

We are required to write a JavaScript function that takes in one such object. The function should merge part1 and part2 of the object to form an array of objects like this −

const output = [    {"id": 1, "a": 50, "b": 40},    {"id": 2, "a": 55},    {"id": 3, "b": 45},    {"id": 4, "a": 100, "b": 110} ];

Example

The code for this will be −

const obj = {    "part1": [{"id": 1, "a": 50},{"id": 2, "a": 55},{"id": 4, "a": 100}],    "part2":[{"id": 1, "b": 40}, {"id": 3, "b": 45}, {"id": 4, "b": 110}] }; const mergeObject = (obj = {}) => {    let result = [];    result = Object.keys(obj).reduce(function (hash) {       return function (r, k) {          obj[k].forEach(function (o) {             if (!hash[o.id]) {                hash[o.id] = {};                r.push(hash[o.id]);             }             Object.keys(o).forEach(function (l) {                hash[o.id][l] = o[l];             });          });          return r;       };    }(Object.create(null)), []).sort((a, b) => {       return a['id'] − b['id'];    });    return result; }; console.log(mergeObject(obj));

Output

And the output in the console will be −

[    { id: 1, a: 50, b: 40 },    { id: 2, a: 55 },    { id: 3, b: 45 },    { id: 4, a: 100, b: 110 } ]