Here is a tutorial on how to use the spread operator:

What is the function of the Spread Operator: clone a data but do not affect the original data

1./Copy 1 array

for an array let arr=[1,2,3,4]; To copy the normal array arr, we do the following let copy =arr

console.log( copy) //[1,2,3,4] If we use Spread Operator, we use the following let copy =[…arr] console.log( copy)//[1,2,3,4]

if you are missing the … in the array, what will happen:

it’s array in array let copy=[[1,2,3,4]], not [1,2,3,4] We see the above 2 ways are the same

2./ join 2 arrays together (Concatenate arrays)

To join any two arrays together in JavaScript, we have a way like using function concat(), code result if using spread operation : result

We see the two results are the same.

Copy an object

To copy an object in the usual way, what will we use?

if using Spread Operator then

don’t forget the sign … if you forget, the data will be

object in object

Merge objects together

To concatenate 2 or more objects together, we will use the function object.assign() to do it as follows:

when using the Spread Operator: note when there are 2 data that have the same key: age has 2 data, age :25 and age: 332, because when concatenating, we let employee = {…person,…job, }; so age :332 is behind, so take the following value

and if let employee = { …job,…person,}; then age : 25

note: when using Spread Operator : what data is … that data

you have array you use for array, you have obj you use for obj can’t attach obj to arr like the example below