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5 ways - unique values in array

JavaScript ES 6

unique-values-in-array.js Raw #

const arr = [
	'banan',
	'apple',
	'orange',
	'lemon',
	'apple',
	'lemon',
]

// 1 no duplicities filter
function removeDuplicities(data) {
	return 	data.filter((value, index) => data.indexOf(value) === index)
}

// 1 only duplicities filter
function onlyDuplicities(data) {
	return 	data.filter((value, index) => data.indexOf(value) !== index)
}


// 2 set
[...new Set(arr)]



// 3 forEeach
let unique = []
arr.forEach(item => {
	if (!unique.includes(item)) {
		unique.push(item)
	}
})



// 4 reduce #1
let unique = arr.reduce((acc, curr) => {
	if (acc.indexOf(curr) < 0) {
		acc.push(curr)
	}
	return acc
}, [])



// 4 reduce #2
let unique = arr.reduce((acc, curr) => {
	return acc.includes(curr) ? acc : [...acc, curr]
}, [])


// 5  prototype #1
Array.prototype.unique = function() {
	let unique = []

	this.forEach((item) => {
	  if (!unique.includes(item)) {
		unique.push(item)
	  }	
	})
	return unique
}


// 5  prototype #2
Array.prototype.unique = function() {
	return [...(new Set(this))] // or Array.from() instead of [...]
}