How to CRUD an Array in JavaScript

Updated at August 21, 2020

There are two ways to create, update, and delete items to an array in JavaScript. The first approach is by using the mutable methods which will change the array itself.

The second approach is by using the immutable methods, which will return a new array that contains a new updated value. This could be very useful if your using Redux or changing component state in React.

Let's say we have an array that contains a few items.

const list = ["Item 1", "Item 2", "Item 3"]

Create item

The mutable way:

const newItem = "Item 4"

list.push(newItem)

The immutable way:

const newItem = "Item 4"

const newList = list.concat([newItem])

Result:

[
  "Item 1",
  "Item 2",
  "Item 3",
  "Item 4"
]

Update item

The mutable way:

const itemIndex = 1
const newItem = "Item 2 (updated)"

list[itemIndex] = newItem

The immutable way:

const itemIndex = 1
const newItem = "Item 2 (updated)"

const newList = list.map((item, index) => {
	return index === itemIndex ? newItem : item
})

Result:

[
  "Item 1",
  "Item 2 (updated)",
  "Item 3"
]

Delete item

The mutable way:

const itemIndex = 1

list.splice(itemIndex, 1)

The immutable way:

const itemIndex = 1

const newList = list.filter((item, index) => {
	return index !== itemIndex
})

Result:

[
  "Item 1",
  "Item 3"
]

Rahman Fadhil

I'm a software engineer specialized in iOS and full-stack web development. I can help you to learn new skills and solve your coding problems in Codementor.

Codementor badge