Combine strings algorithm.

Combine.js

/**
 * Combine algorithm.
 * 
 * @author Sergey Kamardin <[email protected]>
 * 
 * Usage:
 * 
 * combine(['a','b'])
 * 
 * Will return ['ab', 'ba'];
 * 
 * Also possible to pass object agains Array, which can content params: atoms, combiner, regexp.
 *  - atoms is a symbols array (like ['a','b']);
 *  - combiner is a function, that will be called each time, when need to concat two symbols.
 *    If this function return string or array, it will be added to the final result, if another type, then not.
 *  - regexp is a sprintf style template (only with %s) that will be converted to check dobules in result set. 
 * 
 */
function combine(context) {
    var atoms, molecules, level,
        regexp = '%s',
        combiner = function(one, two) {
            return [one, two].join('')
        };

    // Options initialization
    if (Object.prototype.toString.call(context) == '[object Array]') {
        atoms     = context;
        molecules = atoms.slice();
        level     = atoms.length;
    } else {
        atoms     = context.atoms;
        molecules = context.molecules || context.atoms.slice();
        level     = context.level     || context.atoms.length;
        combiner  = context.combiner  || combiner;
        regexp    = context.regexp  || regexp;
    }

    // Need to calculate the deep of recursion for stop in the future.
    level--;

    var response = [];

    if (level == 0) return response;

    $.each(molecules, function(i, molecula) {
        var iterationResult = [];

        $.each(atoms, function(i, atom) {
            var test = new RegExp(regexp.replace('%s', atom));

            if (!test.test(molecula)) {
                var result = combiner.call(null, molecula, atom);
                if (typeof result == 'string') iterationResult.push(result);
                if (Object.prototype.toString.call(result) == '[object Array]') $.merge(iterationResult, result);
            }
        });

        $.merge(iterationResult, combine({atoms: atoms, molecules: iterationResult, level: level, combiner: combiner}));

        $.merge(response, iterationResult);
    });

    return response;
};