Index: lib/Format/Format.cpp
===================================================================
--- lib/Format/Format.cpp
+++ lib/Format/Format.cpp
@@ -1528,7 +1528,8 @@
 static FormatStyle::LanguageKind getLanguageByFileName(StringRef FileName) {
   if (FileName.endswith(".java")) {
     return FormatStyle::LK_Java;
-  } else if (FileName.endswith_lower(".js")) {
+  } else if (FileName.endswith_lower(".js") || FileName.endswith_lower(".ts")) {
+    // JavaScript or TypeScript.
     return FormatStyle::LK_JavaScript;
   } else if (FileName.endswith_lower(".proto") ||
              FileName.endswith_lower(".protodevel")) {
Index: tools/clang-format/clang-format-diff.py
===================================================================
--- tools/clang-format/clang-format-diff.py
+++ tools/clang-format/clang-format-diff.py
@@ -48,7 +48,7 @@
                       help='custom pattern selecting file paths to reformat '
                       '(case sensitive, overrides -iregex)')
   parser.add_argument('-iregex', metavar='PATTERN', default=
-                      r'.*\.(cpp|cc|c\+\+|cxx|c|cl|h|hpp|m|mm|inc|js|proto'
+                      r'.*\.(cpp|cc|c\+\+|cxx|c|cl|h|hpp|m|mm|inc|js|ts|proto'
                       r'|protodevel|java)',
                       help='custom pattern selecting file paths to reformat '
                       '(case insensitive, overridden by -regex)')