Slice Vs Splice Javascript Mdn

Slice Vs Splice Javascript Mdn

5 min read Jun 20, 2024
Slice Vs Splice Javascript Mdn

Slice vs Splice: The Key Differences in JavaScript

Both slice() and splice() are powerful methods in JavaScript used to manipulate arrays. While they seem similar at first glance, understanding their distinct functionalities is crucial for effective array management. This article will delve into the differences between slice() and splice(), highlighting their applications and providing clear examples.

slice(): Extracting a Portion of an Array

The slice() method, as its name suggests, extracts a portion of an array, creating a new array with the selected elements. It does not modify the original array. Here's how it works:


array.slice(start, end);
  • start: The index where the extraction begins. This index is inclusive.
  • end: The index where the extraction ends. This index is exclusive. If omitted, it extracts all elements from start until the end of the array.


const numbers = [1, 2, 3, 4, 5];
const slicedNumbers = numbers.slice(1, 3); // [2, 3]
console.log(slicedNumbers); // Output: [2, 3]
console.log(numbers); // Output: [1, 2, 3, 4, 5] 

In the example above, slice(1, 3) creates a new array slicedNumbers containing elements from index 1 (inclusive) to index 3 (exclusive). The original array numbers remains unchanged.

splice(): Modifying an Array

Unlike slice(), splice() directly modifies the original array. It allows you to add, remove, or replace elements at specific positions.


array.splice(start, deleteCount, item1, item2, ...);
  • start: The index where the modification begins.
  • deleteCount: The number of elements to delete from the starting index.
  • item1, item2, ... (optional): New elements to be inserted at the starting index.


1. Deleting elements:

const fruits = ['apple', 'banana', 'orange', 'mango'];
fruits.splice(1, 2); // Removes 'banana' and 'orange'
console.log(fruits); // Output: ['apple', 'mango']

2. Inserting elements:

const colors = ['red', 'blue'];
colors.splice(1, 0, 'green'); // Inserts 'green' at index 1
console.log(colors); // Output: ['red', 'green', 'blue']

3. Replacing elements:

const animals = ['dog', 'cat', 'bird'];
animals.splice(1, 1, 'monkey'); // Replaces 'cat' with 'monkey'
console.log(animals); // Output: ['dog', 'monkey', 'bird']

Key Differences: A Summary

Feature slice() splice()
Purpose Extract a portion of an array Modify the original array
Original Array Remains unchanged Modified directly
Return Value Returns a new array Returns an array of deleted elements
Arguments start, end (optional) start, deleteCount, item1, ... (optional)


Understanding the differences between slice() and splice() is crucial for effectively manipulating arrays in JavaScript. Use slice() for creating new arrays from existing ones, and splice() for directly modifying the original array by adding, removing, or replacing elements. By mastering these methods, you can confidently and efficiently manage your array data.