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.

if (type == "variable") {register(value); return cont(functiondef);}
    if (type == "(") return cont(pushlex(")"), pushcontext, commasep(funarg, ")"), poplex, statement, popcontext);
  }
  function funarg(type, value) {
    if (type == "variable") {register(value); return isTS ? cont(maybetype) : cont();}
  }
  
  return {
    startState: function(basecolumn) {
      return {
        tokenize: jsTokenBase,
        lastType: null,
        cc: [],
        lexical: new JSLexical((basecolumn || 0) - indentUnit, 0, "block", false),
        localVars: parserConfig.localVars,
        globalVars: parserConfig.globalVars,
        context: parserConfig.localVars && {vars: parserConfig.localVars},
        indented: 0
      };
    },
    token: function(stream, state) {
      if (stream.sol()) {
        if (!state.lexical.hasOwnProperty("align"))
          state.lexical.align = false;
        state.indented = stream.indentation();
      }
      if (stream.eatSpace()) return null;
      var style = state.tokenize(stream, state);
      if (type == "comment") return style;
      state.lastType = type;