diff --git a/src/index.ts b/src/index.ts
index e3f6581..0769507 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -6,8 +6,6 @@ export type JSONValue = true | false | null | string | Number | JSONObject | JSO
 const suspectProtoRx = /"(?:_|\\u005[Ff])(?:_|\\u005[Ff])(?:p|\\u0070)(?:r|\\u0072)(?:o|\\u006[Ff])(?:t|\\u0074)(?:o|\\u006[Ff])(?:_|\\u005[Ff])(?:_|\\u005[Ff])"\s*:/
 const suspectConstructorRx = /"(?:c|\\u0063)(?:o|\\u006[Ff])(?:n|\\u006[Ee])(?:s|\\u0073)(?:t|\\u0074)(?:r|\\u0072)(?:u|\\u0075)(?:c|\\u0063)(?:t|\\u0074)(?:o|\\u006[Ff])(?:r|\\u0072)"\s*:/
 
-const STR_MAP = new Map()
-
 function jsonParseTransform (key: string, value: any): any {
   if (key === '__proto__' || key === 'prototype' || key === 'constructor') {
     return