Index: lib/Format/UnwrappedLineFormatter.h
===================================================================
--- lib/Format/UnwrappedLineFormatter.h
+++ lib/Format/UnwrappedLineFormatter.h
@@ -77,7 +77,8 @@
   /// For example, 'public:' labels in classes are offset by 1 or 2
   /// characters to the left from their level.
   int getIndentOffset(const FormatToken &RootToken) {
-    if (Style.Language == FormatStyle::LK_Java)
+    if (Style.Language == FormatStyle::LK_Java ||
+        Style.Language == FormatStyle::LK_JavaScript)
       return 0;
     if (RootToken.isAccessSpecifier(false) || RootToken.isObjCAccessSpecifier())
       return Style.AccessModifierOffset;
Index: lib/Format/UnwrappedLineParser.cpp
===================================================================
--- lib/Format/UnwrappedLineParser.cpp
+++ lib/Format/UnwrappedLineParser.cpp
@@ -693,7 +693,8 @@
   case tok::kw_public:
   case tok::kw_protected:
   case tok::kw_private:
-    if (Style.Language == FormatStyle::LK_Java)
+    if (Style.Language == FormatStyle::LK_Java ||
+        Style.Language == FormatStyle::LK_JavaScript)
       nextToken();
     else
       parseAccessSpecifier();
@@ -824,7 +825,10 @@
       }
       nextToken();
       if (Line->Tokens.size() == 1) {
-        if (FormatTok->Tok.is(tok::colon)) {
+        if (FormatTok->Tok.is(tok::colon) &&
+            // Colon in class bodies is a typed member variable in JS.
+            (Style.Language != FormatStyle::LK_JavaScript ||
+             !Line->MustBeDeclaration)) {
           parseLabel();
           return;
         }
Index: unittests/Format/FormatTestJS.cpp
===================================================================
--- unittests/Format/FormatTestJS.cpp
+++ unittests/Format/FormatTestJS.cpp
@@ -500,5 +500,15 @@
   verifyFormat("var x: P<string, (a: number) => string>;");
 }
 
+TEST_F(FormatTestJS, ClassDeclarations) {
+  verifyFormat("class C {\n  x: string = 12;\n}");
+  verifyFormat("class C {\n  x(): string => 12;\n}");
+  verifyFormat("class C {\n  ['x' + 2]: string = 12;\n}");
+  verifyFormat("class C {\n  private x: string = 12;\n}");
+  verifyFormat("class C {\n  private static x: string = 12;\n}");
+  verifyFormat("class C {\n  static x(): string { return 'asd'; }\n}");
+  verifyFormat("class C extends P implements I {}");
+}
+
 } // end namespace tooling
 } // end namespace clang