code: function (options) {
      // Parse a string representing a file size and convert it into bytes.
      // A number on it's own will be assumed to be bytes. A multiple such as
      // "k" or "m" can be appended to the string to handle larger numbers. This
      // is case insensitive and uses powers of 1024 rather than (1000).
      // So both 1kB and 1kb == 1024.
      function parseLimit(string) {
        var matches = ('' + string).toLowerCase().match(regexp),
            bytes = null, power;
  
        if (matches) {
          bytes = parseFloat(matches[1]);
          power = powers[matches[2]];
  
          if (bytes && power) {
            bytes = Math.pow(bytes * 1024, power);
          }
        }
  
        return bytes || null;
      }
  
      var powers = { k: 1, m: 2, g: 3, t: 4 },
          regexp = /^(\d+(?:.\d+)?)\s*([kmgt]?)b?$/,
          limit  = options && parseLimit(options.limit);
  
      return function (req, res, next) {
        if (limit) {
          var contentLength = parseInt(req.header('Content-Length', 0), 10),
              message = 'Sorry, the content you have uploaded is larger than JS Bin can handle. Max size is ' + options.limit;
  
          if (limit && contentLength > limit) {
            return next(new errors.RequestEntityTooLarge(message));
          }
        }
        next();
      };
    }
docs: Limit the file size that can be uploaded.