How to remove every Nth element from an array JavaScript?

Removing every Nth element from an array is a common task in JavaScript. This can be accomplished using the Array.prototype.splice() method to modify the array in-place, or by creating a new array with the filtered elements.

Method 1: Using splice() (In-Place Modification)

The splice() method removes elements from the array and modifies the original array:

const arr = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'];
console.log("Original array:", arr);

const removeNth = (arr, n) => {
    // Start from n-1 index and remove every nth element
    // We need to go backwards to avoid index shifting issues
    for(let i = arr.length - 1; i >= 0; i--) {
        if((i + 1) % n === 0) {
            arr.splice(i, 1);
        }
    }
};

removeNth(arr, 3);
console.log("After removing every 3rd element:", arr);

Original array: [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j' ]
After removing every 3rd element: [ 'a', 'b', 'd', 'e', 'g', 'h', 'j' ]

Method 2: Using filter() (Creates New Array)

A more functional approach using filter() that doesn't modify the original array:

const originalArray = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'];
console.log("Original array:", originalArray);

const removeEveryNth = (arr, n) => {
    return arr.filter((element, index) => (index + 1) % n !== 0);
};

const filteredArray = removeEveryNth(originalArray, 3);
console.log("New array (every 3rd removed):", filteredArray);
console.log("Original unchanged:", originalArray);

Original array: [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j' ]
New array (every 3rd removed): [ 'a', 'b', 'd', 'e', 'g', 'h', 'j' ]
Original unchanged: [ 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j' ]

Practical Example with Numbers

const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];
console.log("Original numbers:", numbers);

// Remove every 4th element (4, 8, 12)
const result = numbers.filter((num, index) => (index + 1) % 4 !== 0);
console.log("After removing every 4th:", result);

Original numbers: [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 ]
After removing every 4th: [ 1, 2, 3, 5, 6, 7, 9, 10, 11 ]

Comparison

Conclusion

Use filter() for a functional approach that preserves the original array, or splice() when you need to modify the array in-place. The filter method is generally preferred for its immutability.