code: function parseParameter(spec, ctx, params) {
    if (!spec || !isObject(spec)) return spec;
  
    for (var i=0, n=PARSERS.length, p; i<n; ++i) {
      p = PARSERS[i];
      if (spec.hasOwnProperty(p.key)) {
        return p.parse(spec, ctx, params);
      }
    }
    return spec;
  }
docs: Parse a single parameter.