How can we remove duplicate entries from a JavaScript Array?

You can remove duplicate entries from a JavaScript array using various methods and techniques. Here are several approaches to accomplish this:

Using Set (ES6):

The easiest way to remove duplicates from an array in modern JavaScript is by converting the array into a Set and then converting it back to an array.

const arrayWithDuplicates = [1, 2, 2, 3, 4, 4, 5]; const uniqueArray = [...new Set(arrayWithDuplicates)];

Using a For Loop:

You can manually iterate through the array and build a new array containing only unique elements.

const arrayWithDuplicates = [1, 2, 2, 3, 4, 4, 5]; const uniqueArray = []; for (const item of arrayWithDuplicates) { if (!uniqueArray.includes(item)) { uniqueArray.push(item); } }
Using filter():
You can use the filter() method to create a new array with only unique elements.
const arrayWithDuplicates = [1, 2, 2, 3, 4, 4, 5]; const uniqueArray = arrayWithDuplicates.filter((value, index, self) => self.indexOf(value) === index);
Using reduce():
The reduce() method can also be used to remove duplicates while iterating through the array.
const arrayWithDuplicates = [1, 2, 2, 3, 4, 4, 5]; const uniqueArray = arrayWithDuplicates.reduce((accumulator, currentValue) => { if (!accumulator.includes(currentValue)) { accumulator.push(currentValue); } return accumulator; }, []);
Using a Custom Function:
You can create a custom function to remove duplicates by iterating through the array and checking for duplicate elements.
function removeDuplicates(arr) { const uniqueArray = []; for (const item of arr) { if (!uniqueArray.includes(item)) { uniqueArray.push(item); } } return uniqueArray; }
const arrayWithDuplicates = [1, 2, 2, 3, 4, 4, 5]; const uniqueArray = removeDuplicates(arrayWithDuplicates);
Using Libraries:
There are also libraries like Lodash that provide utility functions, such as _.uniq() to remove duplicates from an array.
const _ = require('lodash'); const arrayWithDuplicates = [1, 2, 2, 3, 4, 4, 5]; const uniqueArray = _.uniq(arrayWithDuplicates);
Choose the method that best suits your needs and the JavaScript environment you are working in. The Set method is the most concise and efficient for modern browsers, but the other methods are still useful for older browsers or when you need more control over the process.