docs: function getSource(fn, altSource) {
      var result = altSource;
      if (isStringable(fn)) {
        result = String(fn);
      } else if (support.decompilation) {
        // escape the `{` for Firefox 1
        result = (/^[^{]+\{([\s\S]*)}\s*$/.exec(fn) || 0)[1];
      }
      return (result || '').replace(/^\s+|\s+$/g, '');
    }