Handy JavaScript Snippets

removeDuplicatesInArray.js

// Removes duplicate items from an array.
//
// Credit to this awesome article by Samantha Ming (@samantha_ming)
// https://medium.com/dailyjs/how-to-remove-array-duplicates-in-es6-5daa8789641c

const array = ['🦙', 1, 1, 2, '🦙', '🦙', 3];

// Using Set (requires ES6)
let uniqueSet = new Set(array);
let arrayFromSet = [...uniqueSet];


// Using Array.filter()
let filteredArray = array.filter(function(item, index) {
	return array.indexOf(item) === index;
});

// or, with ES6 support, using an arrow function to shorten
let filteredArrayES6 = array.filter((item, index) => array.indexOf(item) === index);


// Using Array.reduce()
let reducedArray = array.reduce(function(accumulator, currentItem) {
	if (accumulator.indexOf(currentItem) === -1) {
		accumulator.push(currentItem);
	}
	return accumulator;
}, []);

// or, with ES6 support, using an arrow function and Array.includes()
let reducedArrayES6 = array.reduce((accumulator, currentItem) => {
	return unique.includes(currentItem) ? accumulator : [...accumulator, currentItem]
}, []);