How to Use Slice in JavaScript Array: Simple Guide

Use the slice(start, end) method on a JavaScript array to get a new array containing elements from the start index up to but not including the end index. If end is omitted, it slices until the end of the array.

Syntax

The slice method is called on an array and takes two optional parameters:

• start: The index where slicing begins (inclusive). Defaults to 0 if omitted.
• end: The index where slicing ends (exclusive). Defaults to the array's length if omitted.

The method returns a new array with the selected elements and does not change the original array.

javascript

array.slice(start, end)

Example

This example shows how to use slice to get parts of an array without changing the original array.

javascript

const fruits = ['apple', 'banana', 'cherry', 'date', 'elderberry'];

const part1 = fruits.slice(1, 3); // from index 1 to 2
const part2 = fruits.slice(2);    // from index 2 to end

console.log(part1);
console.log(part2);
console.log(fruits);

Output

[ 'banana', 'cherry' ]
[ 'cherry', 'date', 'elderberry' ]
[ 'apple', 'banana', 'cherry', 'date', 'elderberry' ]

Common Pitfalls

Common mistakes when using slice include:

• Forgetting that the end index is exclusive, so the element at end is not included.
• Using negative indexes incorrectly. Negative values count from the end of the array.
• Expecting slice to modify the original array—it does not.

javascript

const numbers = [10, 20, 30, 40, 50];

// Wrong: expecting element at index 3 included
const wrongSlice = numbers.slice(1, 3);
console.log(wrongSlice); // Outputs [20, 30], not including 40

// Correct: to include element at index 3, use end as 4
const correctSlice = numbers.slice(1, 4);
console.log(correctSlice); // Outputs [20, 30, 40]

// Using negative indexes
const negativeSlice = numbers.slice(-3, -1);
console.log(negativeSlice); // Outputs [30, 40]

Output

[ 20, 30 ]
[ 20, 30, 40 ]
[ 30, 40 ]

Quick Reference

Remember these key points about slice:

• Returns a new array without changing the original.
• start is inclusive, end is exclusive.
• Negative indexes count from the end.
• If end is omitted, slices to the end.

Key Takeaways

Use slice(start, end) to get a part of an array without changing the original.

start index is included, but end index is excluded in the result.

Negative indexes count from the end of the array.

If you omit end, slicing continues to the array's end.

slice always returns a new array.