From 09a164cac9c80c6c8b251b5f0fd4072c2d220e87 Mon Sep 17 00:00:00 2001
From: reluc <relu.cri@gmail.com>
Date: Wed, 18 Mar 2026 17:00:28 +0100
Subject: [PATCH] feat(isJson): allow any valid JSON value to pass (rfc8259)

fix #2183
---
 README.md               |  2 +-
 src/lib/isJSON.js       |  9 ++++++++-
 test/validators.test.js | 23 +++++++++++++++++++++++
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index fe57761a5..107684d29 100644
--- a/README.md
+++ b/README.md
@@ -137,7 +137,7 @@ Validator                               | Description
 **isISO4217(str)**                      | check if the string is a valid [ISO 4217][ISO 4217] officially assigned currency code.
 **isISRC(str)**                         | check if the string is an [ISRC][ISRC].
 **isISSN(str [, options])**             | check if the string is an [ISSN][ISSN].<br/><br/>`options` is an object which defaults to `{ case_sensitive: false, require_hyphen: false }`. If `case_sensitive` is true, ISSNs with a lowercase `'x'` as the check digit are rejected.
-**isJSON(str [, options])**             | check if the string is valid JSON (note: uses JSON.parse).<br/><br/>`options` is an object which defaults to `{ allow_primitives: false }`. If `allow_primitives` is true, the primitives 'true', 'false' and 'null' are accepted as valid JSON values.
+**isJSON(str [, options])**             | check if the string is valid JSON (note: uses JSON.parse).<br/><br/>`options` is an object which defaults to `{ allow_primitives: false, allow_any_value: false }`. If `allow_primitives` is true, the primitives 'true', 'false' and 'null' are accepted as valid JSON values. If `allow_any_value` is true, any string that passes JSON.parse is cosidered valid.
 **isJWT(str)**                          | check if the string is valid JWT token.
 **isLatLong(str [, options])**          | check if the string is a valid latitude-longitude coordinate in the format `lat,long` or `lat, long`.<br/><br/>`options` is an object that defaults to `{ checkDMS: false }`. Pass `checkDMS` as `true` to validate DMS(degrees, minutes, and seconds) latitude-longitude format.
 **isLength(str [, options])**           | check if the string's length falls in a range and equal to any of the integers of the `discreteLengths` array if provided.<br/><br/>`options` is an object which defaults to `{ min: 0, max: undefined, discreteLengths: undefined }`. Note: this function takes into account surrogate pairs.
diff --git a/src/lib/isJSON.js b/src/lib/isJSON.js
index 5c51dd31c..a59d25a61 100644
--- a/src/lib/isJSON.js
+++ b/src/lib/isJSON.js
@@ -4,18 +4,25 @@ import merge from './util/merge';
 
 const default_json_options = {
   allow_primitives: false,
+  allow_any_value: false,
 };
 
 export default function isJSON(str, options) {
   assertString(str);
   try {
     options = merge(options, default_json_options);
+    const obj = JSON.parse(str);
+
+    // Strict RFC validation anything that parse is JSON
+    if (options.allow_any_value) {
+      return true;
+    }
+
     let primitives = [];
     if (options.allow_primitives) {
       primitives = [null, false, true];
     }
 
-    const obj = JSON.parse(str);
     return includes(primitives, obj) || (!!obj && typeof obj === 'object');
   } catch (e) { /* ignore */ }
   return false;
diff --git a/test/validators.test.js b/test/validators.test.js
index 1fa629092..4279a2ede 100644
--- a/test/validators.test.js
+++ b/test/validators.test.js
@@ -7238,6 +7238,29 @@ describe('Validators', () => {
     });
   });
 
+  it('should validate JSON with any value', () => {
+    test({
+      validator: 'isJSON',
+      args: [{ allow_any_value: true }],
+      valid: [
+        '{ "key": "value" }',
+        '{}',
+        'null',
+        'false',
+        'true',
+        '"RFC8259"',
+        '42',
+      ],
+      invalid: [
+        '{ key: "value" }',
+        '{ \'key\': \'value\' }',
+        '{ "key": value }',
+        '01234',
+        "'nope'",
+      ],
+    });
+  });
+
   it('should validate multibyte strings', () => {
     test({
       validator: 'isMultibyte',