scan.js

module.exports = function scanEach(redis, opts, eachFn, callback) {
  var scan_args = [ opts.cursor || 0 ];

  if (opts.prefix) scan_args.push('MATCH', opts.prefix);
  if (opts.count) scan_args.push('COUNT', opts.count);

  scan_args.push(function (err, results) {
    if (err) return callback(err);
    if (!Array.isArray(results)) return callback(new Error('Invalid results from redis SCAN command'));

    var nextCursor = parseInt(results.shift() || 0, 10);
    var items = results.shift() || [];

    if (!items.length && !nextCursor) return callback();

    var nextScan = {
      cursor: nextCursor,
      prefix: opts.prefix,
      count: opts.count
    };

    if (items.length) eachFn(results.shift() || [], function (err) {
      if (err) return callback(err);

      if (!nextCursor) return callback();
      scanEach(redis, nextScan, eachFn, callback);
    });
    else scanEach(redis, nextScan, eachFn, callback);
  });

  // console.log(scan_args);
  redis.scan.apply(redis, scan_args);
};