[javascript mode] Accept modifiers before parameters in TypeScript mode

Closes #4916

Author: marijnh

mode/javascript/javascript.js

@@ -55,6 +55,7 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
         "private": kw("modifier"),
         "protected": kw("modifier"),
         "abstract": kw("modifier"),
+        "readonly": kw("modifier"),
 
         // types
         "string": type, "number": type, "boolean": type, "any": type
@@ -647,7 +648,7 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
     if (isTS && value == "<") return cont(pushlex(">"), commasep(typeexpr, ">"), poplex, functiondef)
   }
   function funarg(type) {
-    if (type == "spread") return cont(funarg);
+    if (type == "spread" || type == "modifier") return cont(funarg);
     return pass(pattern, maybetype, maybeAssign);
   }
   function classExpression(type, value) {
@@ -665,13 +666,14 @@ CodeMirror.defineMode("javascript", function(config, parserConfig) {
     if (type == "{") return cont(pushlex("}"), classBody, poplex);
   }
   function classBody(type, value) {
-    if (type == "variable" || cx.style == "keyword") {
-      if ((value == "async" || value == "static" || value == "get" || value == "set" ||
-           (isTS && (value == "public" || value == "private" || value == "protected" || value == "readonly" || value == "abstract"))) &&
-          cx.stream.match(/^\s+[\w$\xa1-\uffff]/, false)) {
-        cx.marked = "keyword";
-        return cont(classBody);
-      }
+    if (type == "modifier" || type == "async" ||
+        (type == "variable" &&
+         (value == "static" || value == "get" || value == "set") &&
+         cx.stream.match(/^\s+[\w$\xa1-\uffff]/, false))) {
+      cx.marked = "keyword";
+      return cont(classBody);
+    }
+    if (type == "variable") {
       cx.marked = "property";
       return cont(isTS ? classfield : functiondef, classBody);
     }

mode/javascript/test.js

@@ -346,6 +346,12 @@
   TS("typescript_new_typeargs",
      "[keyword let] [def x] [operator =] [keyword new] [variable Map][operator <][type string], [type Date][operator >]([string-2 `foo${][variable bar][string-2 }`])")
 
+  TS("modifiers",
+     "[keyword class] [def Foo] {",
+     "  [keyword public] [keyword abstract] [property bar]() {}",
+     "  [property constructor]([keyword readonly] [keyword private] [def x]) {}",
+     "}")
+
   var jsonld_mode = CodeMirror.getMode(
     {indentUnit: 2},
     {name: "javascript", jsonld: true}