Index: lib/Format/FormatToken.h
===================================================================
--- lib/Format/FormatToken.h
+++ lib/Format/FormatToken.h
@@ -54,6 +54,7 @@
   TYPE(JsComputedPropertyName) \
   TYPE(JsFatArrow) \
   TYPE(JsTypeColon) \
+  TYPE(JsTypeOperator) \
   TYPE(JsTypeOptionalQuestion) \
   TYPE(LambdaArrow) \
   TYPE(LambdaLSquare) \
Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -141,6 +141,9 @@
          Left->Previous->is(TT_BinaryOperator))) {
       // static_assert, if and while usually contain expressions.
       Contexts.back().IsExpression = true;
+    } else if (Style.Language == FormatStyle::LK_JavaScript && Left->Previous &&
+               Left->Previous->is(Keywords.kw_function)) {
+      Contexts.back().IsExpression = false;
     } else if (Left->Previous && Left->Previous->is(tok::r_square) &&
                Left->Previous->MatchingParen &&
                Left->Previous->MatchingParen->is(TT_LambdaLSquare)) {
@@ -518,6 +521,14 @@
         Tok->Type = TT_InlineASMColon;
       }
       break;
+    case tok::pipe:
+    case tok::amp:
+      // | and & in declarations/type expressions represent union and
+      // intersection types, respectively.
+      if (Style.Language == FormatStyle::LK_JavaScript &&
+          !Contexts.back().IsExpression)
+        Tok->Type = TT_JsTypeOperator;
+      break;
     case tok::kw_if:
     case tok::kw_while:
       if (CurrentToken && CurrentToken->is(tok::l_paren)) {
@@ -2051,6 +2062,8 @@
       return true;
     if (Right.isOneOf(TT_JsTypeColon, TT_JsTypeOptionalQuestion))
       return false;
+    if (Left.is(TT_JsTypeOperator) || Right.is(TT_JsTypeOperator))
+      return false;
     if ((Left.is(tok::l_brace) || Right.is(tok::r_brace)) &&
         Line.First->isOneOf(Keywords.kw_import, tok::kw_export))
       return false;
Index: unittests/Format/FormatTestJS.cpp
===================================================================
--- unittests/Format/FormatTestJS.cpp
+++ unittests/Format/FormatTestJS.cpp
@@ -847,6 +847,14 @@
                getGoogleJSStyleWithColumns(60));
 }
 
+TEST_F(FormatTestJS, UnionIntersectionTypes) {
+  verifyFormat("let x: A|B = A | B;");
+  verifyFormat("let x: A&B|C = A & B;");
+  verifyFormat("let x: Foo<A|B> = new Foo<A|B>();");
+  verifyFormat("function(x: A|B): C&D {}");
+  verifyFormat("function(x: A|B = A | B): C&D {}");
+}
+
 TEST_F(FormatTestJS, ClassDeclarations) {
   verifyFormat("class C {\n  x: string = 12;\n}");
   verifyFormat("class C {\n  x(): string => 12;\n}");