Index: lib/Format/FormatToken.h
===================================================================
--- lib/Format/FormatToken.h
+++ lib/Format/FormatToken.h
@@ -586,6 +586,7 @@
     kw_import = &IdentTable.get("import");
     kw_is = &IdentTable.get("is");
     kw_let = &IdentTable.get("let");
+    kw_type = &IdentTable.get("type");
     kw_var = &IdentTable.get("var");
     kw_yield = &IdentTable.get("yield");
 
@@ -637,6 +638,7 @@
   IdentifierInfo *kw_import;
   IdentifierInfo *kw_is;
   IdentifierInfo *kw_let;
+  IdentifierInfo *kw_type;
   IdentifierInfo *kw_var;
   IdentifierInfo *kw_yield;
 
Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -134,6 +134,10 @@
 
     if (Left->is(TT_OverloadedOperatorLParen)) {
       Contexts.back().IsExpression = false;
+    } else if (Style.Language == FormatStyle::LK_JavaScript &&
+               Line.startsWith(Keywords.kw_type, tok::identifier)) {
+      // type X = (...);
+      Contexts.back().IsExpression = false;
     } else if (Left->Previous &&
         (Left->Previous->isOneOf(tok::kw_static_assert, tok::kw_decltype,
                                  tok::kw_if, tok::kw_while, tok::l_paren,
@@ -147,6 +151,10 @@
                                               Keywords.kw_function)))) {
       // function(...) or function f(...)
       Contexts.back().IsExpression = false;
+    } else if (Style.Language == FormatStyle::LK_JavaScript && Left->Previous &&
+               Left->Previous->is(TT_JsTypeColon)) {
+      // let x: (SomeType);
+      Contexts.back().IsExpression = false;
     } else if (Left->Previous && Left->Previous->is(tok::r_square) &&
                Left->Previous->MatchingParen &&
                Left->Previous->MatchingParen->is(TT_LambdaLSquare)) {
@@ -913,6 +921,9 @@
   void modifyContext(const FormatToken &Current) {
     if (Current.getPrecedence() == prec::Assignment &&
         !Line.First->isOneOf(tok::kw_template, tok::kw_using, tok::kw_return) &&
+        // Type aliases use `type X = ...;` in TypeScript.
+        !(Style.Language == FormatStyle::LK_JavaScript &&
+          Line.startsWith(Keywords.kw_type, tok::identifier)) &&
         (!Current.Previous || Current.Previous->isNot(tok::kw_operator))) {
       Contexts.back().IsExpression = true;
       if (!Line.startsWith(TT_UnaryOperator)) {
Index: unittests/Format/FormatTestJS.cpp
===================================================================
--- unittests/Format/FormatTestJS.cpp
+++ unittests/Format/FormatTestJS.cpp
@@ -914,6 +914,12 @@
   verifyFormat("function(x: A|B = A | B): C&D {}");
   verifyFormat("function x(path: number|string) {}");
   verifyFormat("function x(): string|number {}");
+  verifyFormat("type Foo = Bar|Baz;");
+  verifyFormat("type Foo = Bar<X>|Baz;");
+  verifyFormat("type Foo = (Bar<X>|Baz);");
+  verifyFormat("let x: Bar|Baz;");
+  verifyFormat("let x: Bar<X>|Baz;");
+  verifyFormat("let x: (Foo|Bar)[];");
 }
 
 TEST_F(FormatTestJS, ClassDeclarations) {