[javascript mode] Recognize TypeScript typeof in type position

Closes codemirror#5275

Author: marijnh

mode/javascript/javascript.js

@@ -560,14 +560,13 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
     }
   }
   function typeexpr(type, value) {
+    if (value == "keyof" || value == "typeof") {
+      cx.marked = "keyword"
+      return cont(value == "keyof" ? typeexpr : expression)
+    }
     if (type == "variable" || value == "void") {
-      if (value == "keyof") {
-        cx.marked = "keyword"
-        return cont(typeexpr)
-      } else {
-        cx.marked = "type"
-        return cont(afterType)
-      }
+      cx.marked = "type"
+      return cont(afterType)
     }
     if (type == "string" || type == "number" || type == "atom") return cont(afterType);
     if (type == "[") return cont(pushlex("]"), commasep(typeexpr, "]", ","), poplex, afterType)