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Posted on • Updated on • Originally published at capscode.in

List of uses of spread operator

Hello everyone,

In this tutorial we are going to explain all the uses of SPREAD OPERATOR in JavaScript.

So without wasting much time,, lets get started.
Below are the uses:

• Copying an array
• Concatenating or combining arrays
• Using Math functions
• Using an array as arguments
• Adding elements in array from other array(or pushing array to an array)
• Merging object
• Copying an Object
• Converting HTMLCollections to array
• Converting string to character
• Remove duplicates from an array and create an array of unique elements

1. Copying an array

``````var arr = [1,2,3,4,5,6,7]
var copy_arr = arr

console.log(arr) //[1, 2, 3, 4, 5, 6, 7]
console.log(copy_arr) //[1, 2, 3, 4, 5, 6, 7]
console.log(copy_arr_spread) //[1, 2, 3, 4, 5, 6, 7]
arr.push(8)

console.log(arr) //[1, 2, 3, 4, 5, 6, 7, 8]
console.log(copy_arr) //[1, 2, 3, 4, 5, 6, 7, 8]
console.log(copy_arr_spread) //[1, 2, 3, 4, 5, 6, 7]
``````

2. Concatenating or combining arrays

``````var s1 = ['c','a','p','s']
var s2 = ['c','o','d','e']
var str = [...s1, ...s2]
console.log(str) //["c", "a", "p", "s", "c", "o", "d", "e"]
``````

3. Using Math functions

How we ccan find min or max in array
``````var find_max = [10,20,50, 90,12]
console.log(Math.max(find_max)) //NaN
console.log(Math.max(...find_max)) //90
``````

4. Using an array as arguments

``````function TopThree_Skills(a,b,c){
console.log(`\${a}, \${b}, \${c}`) //c, javascript, reatjs
}

var skills=["c", "javascript", "reatjs", "java", "python", "sql"]
TopThree_Skills(...skills)
``````

5. Adding elements in array from other array

``````var a1 = ['c','o','d','e']
var a2 = ['c','a','p','s', ...a1]
console.log(a2) //["c", "a", "p", "s", "c", "o", "d", "e"]

//some more uses - pushing array to an array
var my_todo_list = ["code","eat","sleep"]

my_todo_list.push(...todo)
console.log(my_todo_list) //["code", "eat", "sleep", "read", "write", "learn"]
``````

6. Merging object

``````var obj1 = {
fname: "John",
lname: "Doe",
}

var obj2 = {
comp: "capscode",
atm_pin: "0000"
}
var obj = {...obj1,...obj2}
console.log(obj) //{fname: "John", lname: "Doe", comp: "capscode", atm_pin: "0000"}
``````

7. Copying an Object

``````var person = {
fname: "John",
lname: "Doe",
}
var myobj_temp = person
var myobj = {...person}

person.phone = "1234567890"

console.log(person) //{fname: "John",lname: "Doe", phone: "1234567890"}
console.log(myobj_temp) //{fname: "John",lname: "Doe", phone: "1234567890"}
console.log(myobj) //{fname: "John",lname: "Doe",}
``````

8. Converiting HTMLCollections to array

``````var doc_arr = [...document.querySelectorAll('div')] //try by writing this in your console
``````

9. Converting string to character

``````var comp = "capscode"
var t=[...comp]
console.log(t) // ["c", "a", "p", "s", "c", "o", "d", "e"]
console.log(...comp) //c a p s c o d e
``````

10. Remove duplicates from an array and create an array of unique elements

``````const list = [1, 3, 1, 3, 3, 2]
const unique = [...new Set(list)]
console.log(unique) //[1,3,2]
``````

if we have missed any point then let us know in the comment.

Hope this post will be helpful for you.
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Thank you,
Team CapsCode