From 2f941f33e238e5fb25e710cb74c35549cd694eb6 Mon Sep 17 00:00:00 2001
From: Ron Buckton <ron.buckton@microsoft.com>
Date: Mon, 13 Nov 2017 16:36:13 -0800
Subject: [PATCH] Make BOM a constant

---
 src/compiler/sys.ts | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index a6e5cd7a392..aa928cdaacd 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -125,6 +125,8 @@ namespace ts {
     };
 
     export let sys: System = (() => {
+        const utf8ByteOrderMark = "\u00EF\u00BB\u00BF";
+
         function getNodeSystem(): System {
             const _fs = require("fs");
             const _path = require("path");
@@ -348,7 +350,7 @@ namespace ts {
             function writeFile(fileName: string, data: string, writeByteOrderMark?: boolean): void {
                 // If a BOM is required, emit one
                 if (writeByteOrderMark) {
-                    data = "\u00EF\u00BB\u00BF" + data;
+                    data = utf8ByteOrderMark + data;
                 }
 
                 let fd: number;
@@ -549,7 +551,7 @@ namespace ts {
                 writeFile(path: string, data: string, writeByteOrderMark?: boolean) {
                     // If a BOM is required, emit one
                     if (writeByteOrderMark) {
-                        data = "\u00EF\u00BB\u00BF" + data;
+                        data = utf8ByteOrderMark + data;
                     }
 
                     ChakraHost.writeFile(path, data);