Right now we use codemirror's JavaScript mode on the website but there's a JSX mode now so we should start using that instead.

getTokenAt: function(pos, precise) {
      var doc = this.doc;
      pos = clipPos(doc, pos);
      var state = getStateBefore(this, pos.line, precise), mode = this.doc.mode;
      var line = getLine(doc, pos.line);
      var stream = new StringStream(line.text, this.options.tabSize);
      while (stream.pos < pos.ch && !stream.eol()) {
        stream.start = stream.pos;
        var style = mode.token(stream, state);
      }
      return {start: stream.start,
              end: stream.pos,
              string: stream.current(),
              className: style || null, 
              type: style || null,
              state: state};
    },
    getTokenTypeAt: function(pos) {
      pos = clipPos(this.doc, pos);
      var styles = getLineStyles(this, getLine(this.doc, pos.line));
      var before = 0, after = (styles.length - 1) / 2, ch = pos.ch;
      if (ch == 0) return styles[2];
      for (;;) {
        var mid = (before + after) >> 1;
        if ((mid ? styles[mid * 2 - 1] : 0) >= ch) after = mid;
        else if (styles[mid * 2 + 1] < ch) before = mid + 1;
        else return styles[mid * 2 + 2];
      }