how to find specific special character from string and replace it to unicode \u0026 + = \u002B

replace only these special character : [$, &, +, #]

example : "HELLO JAMES (WITH ME YOUR) \n+++ SEE & FIELD 4-B +++

MY code

 var char = '+';      
          var saa =char.charCodeAt(0);
          console.log(saa)
          var codeHex = saa.toString(16).toUpperCase();
          while (codeHex.length < 4) {
            codeHex = "0" + codeHex;
        }    
        var afteruni = name.replaceAll('\+','\\u'+codeHex) 

String.prototype.replaceAll = function(search, replacement) {
  var target = this;
  return target.replace(new RegExp(search, 'g'), replacement);
};

i want like this :

"HELLO JAMES (WITH ME YOUR) \n\u002B\u002B\u002B SEE \u0026 FIELD 4-B \u002B\u002B\u002B"

ERROR : Invalid regular expression: /+/: Nothing to repeat\