JS Combinations

combinations.js

const computeCombinations = (items) => {
	let doIt = (rest, start, output) => {
		if (rest.length == 0) {
			output.push(start)
			return
		}
			
		for (let i=0; i < rest.length; i++) {
			let begin = rest.slice(0, i)
			let end = rest.slice(i+1)
			let pick = rest[i]
			let newStart = Array.from(start)
			newStart.push(pick)
			
			doIt(begin.concat(end), newStart, output)
		}
	}
	let output = []
	doIt(items, [], output)
	return output
}

const cards = [1,2,3]
let combinations = computeCombinations(cards)
console.log('Number of combinations: ' + combinations.length)
combinations.forEach(deck => console.log(deck))

output

Number of combinations: 6
[ 1, 2, 3 ]
[ 1, 3, 2 ]
[ 2, 1, 3 ]
[ 2, 3, 1 ]
[ 3, 1, 2 ]
[ 3, 2, 1 ]