feat: add From JS6Chars operation

Adds a new operation to decode JavaScript obfuscated using only 6 characters ([ ] ( ) ! +), commonly known as an esoteric JS encoding style.

- Added src/core/operations/FromJS6Chars.mjs
- Added operation to Code tidy category in Categories.json
- Added tests in tests/operations/tests/FromJS6Chars.mjs

fix: correct invalid input test to check error message output

src/core/config/Categories.json

@@ -521,7 +521,8 @@
             "BSON deserialise",
             "To MessagePack",
             "From MessagePack",
-            "Render Markdown"
+            "Render Markdown",
+            "From JS6Chars"
         ]
     },
     {

src/core/operations/FromJS6Chars.mjs

@@ -0,0 +1,52 @@
+/**
+ * @author Roma476 [friciu.robert09@gmail.com]
+ * @copyright Crown Copyright 2026
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
+
+/**
+ * From JS6Chars operation
+ */
+class FromJS6Chars extends Operation {
+
+    /**
+     * FromJS6Chars constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "From JS6Chars";
+        this.module = "Default";
+        this.description = "Decodes JavaScript that has been obfuscated using only 6 characters: <code>[</code>, <code>]</code>, <code>(</code>, <code>)</code>, <code>!</code> and <code>+</code>. This technique exploits JavaScript's type coercion rules to construct executable code from a minimal character set.<br><br>e.g.  <code>[][(![]+[])[+[]]+...]</code> becomes <code>alert(1)</code>";
+        this.inputType = "string";
+        this.outputType = "string";
+        this.args = [];
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {string}
+     */
+    run(input, args) {
+        // Input Validation
+        for (let i = 0; i < input.length; i++) {
+            const char = input[i];
+            if (!["[", "]", "(", ")", "!", "+"].includes(char)) {
+                throw new OperationError(`Invalid character at position ${i}: ${char}`);
+            }
+        }
+
+        try {
+            return String(Function("\"use strict\"; return (" + input + ")")());
+        } catch (err) {
+            throw new OperationError("Unable to decode: " + err.message);
+        }
+    }
+
+}
+
+export default FromJS6Chars;

tests/operations/tests/FromJS6Chars.mjs

@@ -0,0 +1,56 @@
+/**
+ * FromJS6Chars tests.
+ *
+ * @author Roma476 [friciu.robert09@gmail.com]
+ *
+ * @copyright Crown Copyright 2026
+ * @license Apache-2.0
+ */
+import TestRegister from "../../lib/TestRegister.mjs";
+
+TestRegister.addTests([
+    {
+        name: "From JS6Chars: a",
+        input: "(![]+[])[+!+[]]",
+        expectedOutput: "a",
+        recipeConfig: [
+            {
+                op: "From JS6Chars",
+                args: [],
+            },
+        ],
+    },
+    {
+        name: "From JS6Chars: Hello",
+        input: "[][(![]+[])[+!+[]]+(!![]+[])[+[]]][([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((!![]+[])[+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+!+[]]+([]+[])[(![]+[])[+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(!![]+[])[+[]]+([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]()[+!+[]+[!+[]+!+[]]]+([][(![]+[])[+!+[]]+(!![]+[])[+[]]][([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((!![]+[])[+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+!+[]]+(![]+[+[]])[([![]]+[][[]])[+!+[]+[+[]]]+(!![]+[])[+[]]+(![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+([![]]+[][[]])[+!+[]+[+[]]]+([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(![]+[])[!+[]+!+[]+!+[]]]()[+!+[]+[+[]]]+![]+(![]+[+[]])[([![]]+[][[]])[+!+[]+[+[]]]+(!![]+[])[+[]]+(![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+([![]]+[][[]])[+!+[]+[+[]]]+([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(![]+[])[!+[]+!+[]+!+[]]]()[+!+[]+[+[]]])()[([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((![]+[+[]])[([![]]+[][[]])[+!+[]+[+[]]]+(!![]+[])[+[]]+(![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+([![]]+[][[]])[+!+[]+[+[]]]+([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(![]+[])[!+[]+!+[]+!+[]]]()[+!+[]+[+[]]])+[])[+!+[]]+[+!+[]]+[+!+[]]+[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[!+[]+!+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([]+[])[(![]+[])[+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(!![]+[])[+[]]+([][(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[][(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]()[+!+[]+[!+[]+!+[]]])()",
+        expectedOutput: "Hello",
+        recipeConfig: [
+            {
+                op: "From JS6Chars",
+                args: [],
+            },
+        ],
+    },
+    {
+        name: "From JS6Chars: 123",
+        input: "[+!+[]]+[!+[]+!+[]]+[!+[]+!+[]+!+[]]",
+        expectedOutput: "123",
+        recipeConfig: [
+            {
+                op: "From JS6Chars",
+                args: [],
+            },
+        ],
+    },
+    {
+        name: "From JS6Chars: invalid input",
+        input: "alert(1)",
+        expectedOutput: "Invalid character at position 0: a",
+        recipeConfig: [
+            {
+                op: "From JS6Chars",
+                args: [],
+            },
+        ],
+    },
+]);