gistfile1.txt

'use strict';

var values = ['A', 'B', 'C', 'D'];

function getCombinations(parts) {
    var mix = function(rest) {
            return rest.length === 0 ? '' : rest.join('');
        };
    var combine = function(combinations, firstPart, i, _parts) {
        var rest = _parts.filter(function(part) {
            return firstPart !== part;
        });
        if (rest.length > 0) rest = rest.reduce(combine, []);
        console.log(rest);
        _parts.forEach(function(combination) {
            combinations.push(firstPart + combination.join(''));
        });
        return combinations;
    };
    return parts.reduce(combine, []);
}

console.log(getCombinations(values));