JavaScript merging objects by id

Question

What\'s the correct way to merge two arrays in Javascript?

I\'ve got two arrays (for example):

var a1 = [{ id : 1, name : \"test\"}, { id : 2, name :         


        

Answer 1

ES6 simplifies this:

let merge = (obj1, obj2) => ({...obj1, ...obj2});

Note that repeated keys will be merged, and the value of the second object will prevail and the repeated value of the first object will be ignored.

Example:

let obj1 = {id: 1, uniqueObj1Key: "uniqueKeyValueObj1", repeatedKey: "obj1Val"};
let obj2 = {id: 1, uniqueObj2Key: "uniqueKeyValueObj2", repeatedKey: "obj2Val"};

merge(obj1, obj2)
// {id: 1, uniqueObj1Key: "uniqueKeyValueObj1", repeatedKey: "obj2Val", uniqueObj2Key: "uniqueKeyValueObj2"}
merge(obj2, obj1)
// {id: 1, uniqueObj2Key: "uniqueKeyValueObj2", repeatedKey: "obj1Val", uniqueObj1Key: "uniqueKeyValueObj1"}

Complete solution (with Lodash, not Underscore)

var a1 = [{ id : 1, name : "test"}, { id : 2, name : "test2"}]
var a2 = [{ id : 1, count : "1"}, {id : 2, count : "2"}]
var merge = (obj1, obj2) => ({...obj1, ...obj2});
_.zipWith(a1, a2, merge)
(2) [{…}, {…}]
   0: {id: 1, name: "test", count: "1"}
   1: {id: 2, name: "test2", count: "2"}

If you have an array of arrays to merge you can do it like this:

var arrayOfArraysToMerge = [a1, a2, a3, a4]; //a3 and a4 are arrays like a1 and a2 but with different properties and same IDs.
_.zipWith(...arrayOfArraysToMerge, merge)
(2) [{…}, {…}]
   0: {id: 1, name: "test", count: "1", extra1: "val1", extra2: 1}
   1: {id: 2, name: "test2", count: "2", extra1: "val2", extra2: 2}