permutation

permutation.js

function permutation(arr, choosen, res) {
	if (arr.length === 0) {
		let b = []
		Object.assign(b, choosen)
		res.push(b)
		return
	}

	for (var i = arr.length - 1; i >= 0; i--) {
		// choose
		var tmp = arr[i]
		choosen.push(tmp)
		arr.splice(i, 1)

		// explore
		permutation(arr, choosen, res)

		// un-choose
		choosen.splice(choosen.length - 1, 1)
		arr.splice(i, 0, tmp)
	}
}

let res = []
permutation(["a", "b", "c"], [], res)
console.log(res)