How to merge object in javascript

suppose that we have an user object with different values that we will want to merge or updated in the single object:

const user = {
    name: 'John Doe',
    city:'Abidjan',
    job:'web developper'
}

const same_user = {
    name: 'John Doe',
    city:'Abidjan',
    age:24,
    color:'black',
    hobbies:'football'
}

Now, the first question that we ask ourselves is: How to do that ?

We're going to use the spread operator method to do that. The syntax is three dots (...)

const users = {...user, ...same_user}

The spread operator is a new way to spread iterable element or often expand an iterable like array, object.

Now we are going to see the new users object in our NodeJS REPL:

console.log(users)
{ name: 'John Doe', city:'Abidjan', job:'web developper', age:24, color:'black', hobbies:'football' }

Note that this operator was introduced in ES6.

Comments

[Amin]

It is worth noting that this is a shallow merge. Meaning that nested objects won't get merged but erased with the latter ones using the spread operator.

// https://repl.it/repls/CluelessSpectacularOrder
"use strict";

const a = {
    first: true,
    second: {
        third: true
    }
};

const b = {
    first: true,
    second: {
        fourth: true
    }
};

const merged = {...a, ...b};

console.log(JSON.stringify(merged, null, 2));

/*

{
  "first": true,
  "second": {
    "fourth": true (does not include third!!!)
  }
}

*/

[Emmanuel Dalougou]

The trouble is that here he will check the value of each key. once the value of a key is different from the previous one then it will remove the old value to keep the new value. whatever the nested objects it will do the same process