util: improve performance of normalizeEncoding

PR-URL: #50721
Reviewed-By: Marco Ippolito <[email protected]>
Reviewed-By: Vinícius Lourenço Claro Cardoso <[email protected]>

Author: kylo5aby

lib/internal/util.js

@@ -220,13 +220,13 @@ function slowCases(enc) {
     case 4:
       if (enc === 'UTF8') return 'utf8';
       if (enc === 'ucs2' || enc === 'UCS2') return 'utf16le';
-      enc = `${enc}`.toLowerCase();
+      enc = StringPrototypeToLowerCase(enc);
       if (enc === 'utf8') return 'utf8';
       if (enc === 'ucs2') return 'utf16le';
       break;
     case 3:
       if (enc === 'hex' || enc === 'HEX' ||
-          `${enc}`.toLowerCase() === 'hex')
+      StringPrototypeToLowerCase(enc) === 'hex')
         return 'hex';
       break;
     case 5:
@@ -235,7 +235,7 @@ function slowCases(enc) {
       if (enc === 'UTF-8') return 'utf8';
       if (enc === 'ASCII') return 'ascii';
       if (enc === 'UCS-2') return 'utf16le';
-      enc = `${enc}`.toLowerCase();
+      enc = StringPrototypeToLowerCase(enc);
       if (enc === 'utf-8') return 'utf8';
       if (enc === 'ascii') return 'ascii';
       if (enc === 'ucs-2') return 'utf16le';
@@ -245,23 +245,23 @@ function slowCases(enc) {
       if (enc === 'latin1' || enc === 'binary') return 'latin1';
       if (enc === 'BASE64') return 'base64';
       if (enc === 'LATIN1' || enc === 'BINARY') return 'latin1';
-      enc = `${enc}`.toLowerCase();
+      enc = StringPrototypeToLowerCase(enc);
       if (enc === 'base64') return 'base64';
       if (enc === 'latin1' || enc === 'binary') return 'latin1';
       break;
     case 7:
       if (enc === 'utf16le' || enc === 'UTF16LE' ||
-          `${enc}`.toLowerCase() === 'utf16le')
+      StringPrototypeToLowerCase(enc) === 'utf16le')
         return 'utf16le';
       break;
     case 8:
       if (enc === 'utf-16le' || enc === 'UTF-16LE' ||
-        `${enc}`.toLowerCase() === 'utf-16le')
+      StringPrototypeToLowerCase(enc) === 'utf-16le')
         return 'utf16le';
       break;
     case 9:
       if (enc === 'base64url' || enc === 'BASE64URL' ||
-          `${enc}`.toLowerCase() === 'base64url')
+      StringPrototypeToLowerCase(enc) === 'base64url')
         return 'base64url';
       break;
     default: