Checking for Duplicate Strings in JavaScript Array

JavaScript- Delete all Occurrences in a JS Array

Last Updated : 18 Nov, 2024

These are the following ways to remove all Occurrences of an element in a JS Array:

1. Using filter() method( Simple and Easy for Long Arrays)

The filter() method creates a new array with all elements that passed the test implemented by the given callback function.

JavaScript

function fun(a, e) {
    if (!a.includes(e)) {
        return -1;
    }

    return a.filter(
        (item) => item !== e);
}

const a = [1, 2, 3, 4, 2, 5, 2];
const res = fun(a, 2);

console.log(res);

Output

[ 1, 3, 4, 5 ]

2. Using splice() method(Efficient for Mid range Array)

The splice() method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.

JavaScript

function fun(a, e) {
    if (!a.includes(e)) {
        return -1;
    }

    for (let i = a.length - 1; i >= 0; i--) {
        if (a[i] === e) {
            a.splice(i, 1);
        }
    }
    return a;
}

const a = [1, 2, 3, 4, 2, 5, 2];
const res = fun(a, 2);

console.log(res);

Output

[ 1, 3, 4, 5 ]

3. Using forEach() method (Efficient for Short Array)

The forEach() method will be used to iterate through each element of the array and make changes in it according to the condition passed inside the callback function.

JavaScript

function fun(a, e) {
    if (!a.includes(e)) {
        return -1;
    }

    let a1 = [];
    a.forEach(item => {
        if (item !== e) {
            a1.push(item);
        }
    });
    return a1;
}

const a = [1, 2, 3, 4, 2, 5, 2];
const res = fun(a, 2);
console.log(res);

Output

[ 1, 3, 4, 5 ]

4. Using reduce method(Efficient For Long Arrays)

In this approach we use the reduce method to iterate over each element of the array and accumulate the elements that do not match the element to remove.

JavaScript

function fun(a, e) {
    return a.reduce((acc, c) => {
        if (c !== e) {
            acc.push(c);
        }
        return acc;
    }, []);
}

let a = [1, 2, 3, 4, 2, 5, 2];
let e = 2;
let a1 = fun(a, e);
console.log(a1);

Output

[ 1, 3, 4, 5 ]

Checking for Duplicate Strings in JavaScript Array

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