/*jslint sloppy:true, white:true, vars:true, plusplus:true */

var permutation = function (collection){
    var current,
        subarray,
        result = [],
        currentArray = [],
        newResultArray = [];

    if (collection.length){
        current = collection.shift();
        result = permutation(collection);

        currentArray.push(current);

        result.map(function(list) {
            newResultArray.push(list.slice(0));
            list.push(current);
        });

        result.push(currentArray);
        result = result.concat(newResultArray);
    }

    return result;
};

console.log(permutation(['a','b','c','d'])
            .join('\n'));