JavaScript Array Methods CheatSheet const arr = [ 1 , 2 , 3 , 4 , 5 ] ;
const newArr = [ 6 , 7 , 8 , 9 , 10 ] ;
Methods
Code Example
Result
Return Type
concat()
arr.concat(newArr)
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
array
join()
arr.join('-')
"1-2-3-4-5"
string
pop()
arr.pop()
5
number
push()
arr.push(6)
6
number
reverse()
arr.reverse()
[5, 4, 3, 2, 1]
array
shift()
arr.shift()
1
number
unshift()
arr.unshift(0)
6
number
slice()
arr.slice(1, 4)
[2, 3, 4]
array
splice()
arr.splice(2, 1, 'a', 'b')
[3]
array
indexOf()
arr.indexOf(3)
2
number
lastIndexOf()
arr.lastIndexOf(3)
2
number
includes()
arr.includes(3)
true
boolean
every()
arr.every(num => num > 0)
true
boolean
some()
arr.some(num => num < 0)
false
boolean
filter()
arr.filter(num => num % 2 === 0)
[2, 4]
array
map()
arr.map(num => num * 2)
[2, 4, 6, 8, 10]
array
forEach()
arr.forEach(num => console.log(num))
logs each element
undefined
reduce()
arr.reduce((acc, num) => acc + num, 0)
15
any
find()
arr.find(num => num > 2)
3
any
findIndex()
arr.findIndex(num => num > 2)
2
number
fill()
arr.fill(0, 2, 4)
[1, 2, 0, 0, 5]
array
sort()
arr.sort((a, b) => a - b)
[1, 2, 3, 4, 5]
array
isArray()
Array.isArray(arr)
true
boolean