Refactor fastJsonFormat for high-performance JSON formatting and Unicode decoding

package.json

@@ -18,7 +18,7 @@
   "scripts": {
     "prepack": "npm run test",
     "benchmark": "node benchmark.js",
-    "test": "jest tests/*.spec.js"
+    "test": "jest"
   },
   "devDependencies": {
     "@faker-js/faker": "^9.9.0",

src/constants/index.js

@@ -0,0 +1,41 @@
+/**
+ * Lookup table for structural characters in JSON such as {}[],:"
+ * @type {Uint8Array}
+ */
+const STRUCTURAL_CHARS = new Uint8Array(128);
+
+/**
+ * Lookup table for whitespace characters (tab, newline, carriage return, space)
+ * @type {Uint8Array}
+ */
+const WHITESPACE_CHARS = new Uint8Array(128);
+
+/**
+ * Common JSON structural character codes.
+ * @readonly
+ * @enum {number}
+ */
+const CHAR_CODE = {
+  QUOTE: 34, // "
+  BACKSLASH: 92, // \
+  SLASH: 47, // /
+  OPEN_BRACE: 123, // {
+  CLOSE_BRACE: 125, // }
+  OPEN_BRACKET: 91, // [
+  CLOSE_BRACKET: 93, // ]
+  COMMA: 44, // ,
+  COLON: 58, // :
+};
+
+// Initialize lookup tables
+(() => {
+  /** @type {number[]} JSON structural characters: " , : [ ] { } */
+  const structuralCodes = [34, 44, 58, 91, 93, 123, 125];
+  structuralCodes.forEach((code) => (STRUCTURAL_CHARS[code] = 1));
+
+  /** @type {number[]} Whitespace characters: \t \n \r space */
+  const whitespaceCodes = [9, 10, 13, 32];
+  whitespaceCodes.forEach((code) => (WHITESPACE_CHARS[code] = 1));
+})();
+
+module.exports = { STRUCTURAL_CHARS, WHITESPACE_CHARS, CHAR_CODE };