[javascript mode] Accept strings and numbers as type expressions

Closes #4432

mode/javascript/javascript.js

@@ -539,6 +539,7 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
   }
   function typeexpr(type) {
     if (type == "variable") {cx.marked = "variable-3"; return cont(afterType);}
+    if (type == "string" || type == "number") return cont(afterType);
     if (type == "{") return cont(commasep(typeprop, "}"))
     if (type == "(") return cont(commasep(typearg, ")"), maybeReturnType)
   }
@@ -559,6 +560,7 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
   }
   function afterType(type, value) {
     if (value == "<") return cont(commasep(typeexpr, ">"), afterType)
+    if (value == "|") return cont(typeexpr)
     if (type == "[") return cont(expect("]"), afterType)
   }
   function vardef() {