combinations and permutations

cp.js

function getCombinations(totalChars) {
    var result = []
    var fn = function(prefix, chars) {
        for(let i=0;i<chars.length;i++) {
            result.push(prefix + chars[i])
            fn(prefix + chars[i],chars.slice(i+1))
        }
    }
    fn('',totalChars);
    return result
}

console.log( getCombinations("abc".split("")) )


function getPermutations(str) {
    var result = [];
    var fn = function(prefix,str) {
        for(var i=0;i<str.length;i++) {
            result.push(prefix )
            permutation(prefix + str.charAt(i), str.substring(0,i) + str.substring(i+1,str.length) )
        }
    }

    fn("",str);
    return result;
}