From 2ebe21cf4eaad9200bbb0bbd89e5a7ad95c1a97f Mon Sep 17 00:00:00 2001
From: Long Ho <holevietlong@gmail.com>
Date: Tue, 26 Jan 2021 21:04:39 -0500
Subject: [PATCH] fix(@formatjs/ecma402-abstract): make Set usage IE11-safe,
 fix #2529

---
 packages/ecma402-abstract/IsValidTimeZoneName.ts | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/packages/ecma402-abstract/IsValidTimeZoneName.ts b/packages/ecma402-abstract/IsValidTimeZoneName.ts
index 16686fe7d4..533bb942ba 100644
--- a/packages/ecma402-abstract/IsValidTimeZoneName.ts
+++ b/packages/ecma402-abstract/IsValidTimeZoneName.ts
@@ -14,6 +14,9 @@ export function IsValidTimeZoneName(
   }
 ): boolean {
   const uppercasedTz = tz.toUpperCase();
-  const zoneNames = new Set(Object.keys(tzData).map(z => z.toUpperCase()));
+  const zoneNames = new Set();
+  Object.keys(tzData)
+    .map(z => z.toUpperCase())
+    .forEach(z => zoneNames.add(z));
   return zoneNames.has(uppercasedTz) || uppercasedTz in uppercaseLinks;
 }