Permutations in JavaScript?

Question

I\'m trying to write a function that does the following:

• takes an array of integers as an argument (e.g. [1,2,3,4])
• creates an array of all the possib

Answer 1

This is a very nice use-case for map/reduce:

function permutations(arr) {
    return (arr.length === 1) ? arr :
    arr.reduce((acc, cv, index) => {
        let remaining = [...arr];
        remaining.splice(index, 1);
        return acc.concat(permutations(remaining).map(a => [].concat(cv,a)));
    }, []);
}

• First, we handle the base case and simply return the array if there is only on item in it
• In all other cases
  • we create an empty array
  • loop over the input-array
  • and add an array of the current value and all permutations of the remaining array [].concat(cv,a)