function (str) {
      var strlen = str.length;
      if (this.html.substr(this.currentChar, strlen).toLowerCase() === str.toLowerCase()) {
        this.currentChar += strlen;
        return true;
      }
      return false;
    }
function (str) {
      var strlen = str.length;
      if (this.html.substr(this.currentChar, strlen).toLowerCase() === str.toLowerCase()) {
        this.currentChar += strlen;
        return true;
      }
      return false;
    }
function ( str ) { var strlen = str . length ; if ( this . html . substr ( this . currentChar , strlen ) . toLowerCase ( ) === str . toLowerCase ( ) ) { this . currentChar += strlen ; return true ; } return false ; }
If the current input matches this string, advance the input index;
otherwise, do nothing.

@returns whether input matched string
If the current input matches this string advance the input index ; otherwise do nothing .
Check if the current char is in the string