Array.prototype.pop() by JavaScript convention.
let fruit = ['apple', 'orange', 'banana', 'tomato'];
let popped = fruit.pop();
console.log(popped); // "tomato"
console.log(fruit); // ["apple", "orange", "banana"]Array.prototype.pop() by JavaScript convention.
let fruit = ['apple', 'orange', 'banana', 'tomato'];
let popped = fruit.pop();
console.log(popped); // "tomato"
console.log(fruit); // ["apple", "orange", "banana"]Use splice(startPosition, deleteCount)
array.splice(-1)
var array = ['abc','def','ghi','123'];
var removed = array.splice(-1); //last item
console.log( 'array:', array );
console.log( 'removed:', removed );Videos
Array.prototype.filter will create and return a new array consisting of elements that match the predicate.
function removeByIndex(array, index) {
return array.filter(function (el, i) {
return index !== i;
});
}
Even shorter with ECMAScript 6:
var removeByIndex = (array, index) => array.filter((_, i) => i !== index);
You can use the es6 spread operator and Array.prototype.splice
var arr = [{id:1, name:'name'},{id:2, name:'name'},{id:3, name:'name'}];
let newArr = [...arr]
newArr.splice(index)
The spread operator copies the array and splice changes the contents of an array by removing or replacing existing elements and/or adding new elements
Find the index of the array element you want to remove using indexOf, and then remove that index with splice.
The splice() method changes the contents of an array by removing existing elements and/or adding new elements.
const array = [2, 5, 9];
console.log(array);
const index = array.indexOf(5);
if (index > -1) { // only splice array when item is found
array.splice(index, 1); // 2nd parameter means remove one item only
}
// array = [2, 9]
console.log(array);The second parameter of splice is the number of elements to remove. Note that splice modifies the array in place and returns a new array containing the elements that have been removed.
For completeness, here are functions. The first function removes only a single occurrence (e.g., removing the first match of 5 from [2,5,9,1,5,8,5]), while the second function removes all occurrences:
function removeItemOnce(arr, value) {
var index = arr.indexOf(value);
if (index > -1) {
arr.splice(index, 1);
}
return arr;
}
function removeItemAll(arr, value) {
var i = 0;
while (i < arr.length) {
if (arr[i] === value) {
arr.splice(i, 1);
} else {
++i;
}
}
return arr;
}
// Usage
console.log(removeItemOnce([2,5,9,1,5,8,5], 5))
console.log(removeItemAll([2,5,9,1,5,8,5], 5))In TypeScript, these functions can stay type-safe with a type parameter:
function removeItem<T>(arr: Array<T>, value: T): Array<T> {
const index = arr.indexOf(value);
if (index > -1) {
arr.splice(index, 1);
}
return arr;
}
- Do it simple, intuitive and explicit (Occam's razor)
- Do it immutable (original array stays unchanged)
- Do it with standard JavaScript functions, if your browser doesn't support them - use polyfill
In this code example I use array.filter(...) function to remove unwanted items from an array. This function doesn't change the original array and creates a new one. If your browser doesn't support this function (e.g. Internet Explorer before version 9, or Firefox before version 1.5), consider polyfilling with core-js.
Be mindful though, creating a new array every time takes a big performance hit. If the list is very large (think 10k+ items) then consider using other methods.
Removing item (ECMA-262 Edition 5 code AKA old style JavaScript)
var value = 3
var arr = [1, 2, 3, 4, 5, 3]
arr = arr.filter(function(item) {
return item !== value
})
console.log(arr)
// [ 1, 2, 4, 5 ]Removing item (ECMAScript 6 code)
let value = 3
let arr = [1, 2, 3, 4, 5, 3]
arr = arr.filter(item => item !== value)
console.log(arr)
// [ 1, 2, 4, 5 ]IMPORTANT ECMAScript 6 () => {} arrow function syntax is not supported in Internet Explorer at all, Chrome before version 45, Firefox before version 22, and Safari before version 10. To use ECMAScript 6 syntax in old browsers you can use BabelJS.
Removing multiple items (ECMAScript 7 code)
An additional advantage of this method is that you can remove multiple items
let forDeletion = [2, 3, 5]
let arr = [1, 2, 3, 4, 5, 3]
arr = arr.filter(item => !forDeletion.includes(item))
// !!! Read below about array.includes(...) support !!!
console.log(arr)
// [ 1, 4 ]IMPORTANT array.includes(...) function is not supported in Internet Explorer at all, Chrome before version 47, Firefox before version 43, Safari before version 9, and Edge before version 14 but you can polyfill with core-js.
Removing multiple items (in the future, maybe)
If the "This-Binding Syntax" proposal is ever accepted, you'll be able to do this:
// array-lib.js
export function remove(...forDeletion) {
return this.filter(item => !forDeletion.includes(item))
}
// main.js
import { remove } from './array-lib.js'
let arr = [1, 2, 3, 4, 5, 3]
// :: This-Binding Syntax Proposal
// using "remove" function as "virtual method"
// without extending Array.prototype
arr = arr::remove(2, 3, 5)
console.log(arr)
// [ 1, 4 ]Try it yourself in BabelJS :)
Reference
- Array.prototype.includes
- Functional composition
Hi, I'm mapping over an array to create multiple components and also pass a remove function as a prop to remove itself from the array. The devtools tell me it's working correctly, but visually it is always removing the last element and I have no idea why. I have tried many different ways, but never found a working solution. The code below is a simplified version of my current attempt. Please help!
const array = [
{ id: 0, title: 'one'},
{ id: 1, title: 'two'},
{ id: 2, title: 'three'},
]
const App = () => {
const [items, setItems] = useState(array)
const removeItem = (id) => {
const newItems = items.filter(item => item.id !== id)
setItems(newItems)
}
return (
<>
{items.map(item => (
<Component id={item.id} removeItem={removeItem} />
))}
</>
)
}You're creating two additional arrays: one copyArr and one filtered array. There's no need for both, creating just the filtered array should work fine, eg:
setOriginalArr(
originalArr.filter(item => item !== 'plum')
);
as an example, if originalArr is in state.
Calling .filter on an array doesn't mutate the array it was called on - it returns a new, separate array, so it's safe to use in React without cloning the original array beforehand.
You can use slice() method to extract items from/to specific indexes (without mutation of original array)
let originalArr = ['apple', 'plum', 'berry'];
let sliced = originalArr.slice(1, 2)
console.log(originalArr, sliced)