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.

var bidiRE = /[\u0590-\u05f4\u0600-\u06ff\u0700-\u08ac]/;
    var isNeutral = /[stwN]/, isStrong = /[LRr]/, countsAsLeft = /[Lb1n]/, countsAsNum = /[1n]/;
    
    var outerType = "L";
    return function(str) {
      if (!bidiRE.test(str)) return false;
      var len = str.length, types = [];
      for (var i = 0, type; i < len; ++i)
        types.push(type = charType(str.charCodeAt(i)));
      
      
      
      
      for (var i = 0, prev = outerType; i < len; ++i) {
        var type = types[i];
        if (type == "m") types[i] = prev;
        else prev = type;
      }
      
      
      
      
      
      for (var i = 0, cur = outerType; i < len; ++i) {
        var type = types[i];
        if (type == "1" && cur == "r") types[i] = "n";
        else if (isStrong.test(type)) { cur = type; if (type == "r") types[i] = "R"; }
      }