eslint no-div-regex

• If the regex contains an unescaped ']' before the '=', wrapping '=' in '[=]' alters the character class meaning and may cause incorrect matching or a syntax error.
• If the regex uses a character class that already contains '=' (e.g., '/[=]/'), the fix produces '/[[=]]/' which nests a character class and is invalid syntax.
• If the regex has a flag like 'u' (unicode) and the '=' is part of a Unicode escape sequence (e.g., '/=\u003D/'), the fix breaks the escape by inserting '[=]' before it, changing the matched character.
• If the regex is used in a dynamic context like new RegExp(String(raw)), the source alteration changes the pattern and thus runtime behavior.
• If the regex literal is immediately followed by a comment on the same line without a newline (e.g., '/=foo/#fix'), moving the '=' into a class may disrupt comment parsing if the fixer does not preserve whitespace exactly.
• If the regex is part of a larger expression where operator precedence matters (e.g., 'x += /=foo/ * y'), though unlikely due to prior '/' token, the fix does not alter precedence but the change in literal value could affect results.
• If the regex contains a trailing unescaped '/' before a flag (e.g., '/=/[/]'), the fix does not interfere, but if the original had '/=[]/', the fix yields '/[=][]/' which is valid but may not be intended if the author meant an empty class.
• If the regex is inside a template literal or string that is later evaluated (e.g., `regExpString = "/=foo/"; new RegExp(regExpString)`), the fix does not apply because it's not a literal, so no hazard—but if mistakenly applied via string manipulation, it would corrupt the pattern.

--- orig.js	2026-10-22 14:15:11.723671773 -0400
+++ fixed.js	2026-10-22 14:15:15.194762776 -0400
@@ -1,5 +1,5 @@
 function f() {
   var foo = 1;
-  { let foo = 2; console.log(/=/.test(foo)); }
+  { let foo = 2; console.log(/[=]/.test(foo)); }
 }
 f();

false

--- orig.js	2026-10-22 14:15:11.724671798 -0400
+++ fixed.js	2026-10-22 14:15:15.166762038 -0400
@@ -1,3 +1,3 @@
 let x = 1;
-x *= /=a/.test('ba') + 2;
+x *= /[=]a/.test('ba') + 2;
 console.log(x);

2

--- orig.js	2026-10-22 14:15:11.725671825 -0400
+++ fixed.js	2026-10-22 14:15:14.754751188 -0400
@@ -1,4 +1,4 @@
-function g(a, b = /=/i.test('x'), ...r) {
+function g(a, b = /[=]/i.test('x'), ...r) {
   console.log(arguments.length, b, r.length);
 }
 g(1);

1 false 0

--- orig.js	2026-10-22 14:15:11.726671850 -0400
+++ fixed.js	2026-10-22 14:15:15.243764069 -0400
@@ -1,3 +1,3 @@
 let y
-(/=/.test('x') ? 1 : 0)
+(/[=]/.test('x') ? 1 : 0)
 console.log(y)

undefined

--- orig.js	2026-10-22 14:15:11.726671850 -0400
+++ fixed.js	2026-10-22 14:15:14.031732173 -0400
@@ -1,2 +1,2 @@
 "use strict";
-(function(){ return !/=/.test(''); })();
+(function(){ return !/[=]/.test(''); })();

--- orig.js	2026-10-22 14:15:11.727671877 -0400
+++ fixed.js	2026-10-22 14:15:14.021731910 -0400
@@ -1,5 +1,5 @@
 class C {
-  static rx = /=/;
+  static rx = /[=]/;
   m() { console.log(C.rx.test('x'));
   }
 }

false

--- orig.js	2026-10-22 14:15:15.180762407 -0400
+++ fixed.js	2026-10-22 14:15:18.584852572 -0400
@@ -1,2 +1,2 @@
-let z = /=/i; // flag test
+let z = /[=]/i; // flag test
 console.log(z.test('x'));

false

--- orig.js	2026-10-22 14:15:16.433795494 -0400
+++ fixed.js	2026-10-22 14:15:19.905887797 -0400
@@ -1,6 +1,6 @@
 const obj = {
-  get rx() { return /=/; },
-  getArrow: () => /=/,
-  getFn: function() { return /=;/ }
+  get rx() { return /[=]/; },
+  getArrow: () => /[=]/,
+  getFn: function() { return /[=];/ }
 };
 console.log(obj.getArrow().test('x'), obj.getFn().test('x'));

false false

--- orig.js	2026-10-22 14:15:28.820129009 -0400
+++ fixed.js	2026-10-22 14:15:31.684207772 -0400
@@ -1,7 +1,7 @@
 outer: {
   let result = '';
   inner: {
-    if (/=a/.test('xa')) {
+    if (/[=]a/.test('xa')) {
       break outer;
     }
     result += 'not broken';

--- orig.js	2026-10-22 14:15:28.821129036 -0400
+++ fixed.js	2026-10-22 14:15:31.693208021 -0400
@@ -1,4 +1,4 @@
 let x = 1;
 const y = 2;
-x += /=2/.test('x2') * y;
+x += /[=]2/.test('x2') * y;
 console.log(x);

1

--- orig.js	2026-10-22 14:15:28.822129063 -0400
+++ fixed.js	2026-10-22 14:15:32.372226783 -0400
@@ -1,7 +1,7 @@
 switch (1) {
   case 1:
     function check() {
-      return /=b/.test('ab');
+      return /[=]b/.test('ab');
     }
     console.log(check());
     break;

false

--- orig.js	2026-10-22 14:15:28.823129091 -0400
+++ fixed.js	2026-10-22 14:15:31.653206917 -0400
@@ -1,4 +1,4 @@
-const re = /=🌟/gu;
+const re = /[=]🌟/gu;
 re.lastIndex = 0;
 console.log(re.test('a🌟b'));
 re.lastIndex = 0;

false
null

--- orig.js	2026-10-22 14:15:28.824129118 -0400
+++ fixed.js	2026-10-22 14:15:32.304224902 -0400
@@ -1,5 +1,5 @@
-const raw = /=test/;
+const raw = /[=]test/;
 const re1 = new RegExp(String(raw));
 console.log(re1.test('xtest'));
-const re2 = /=[=]test/;
+const re2 = /[=][=]test/;
 console.log(re2.test('xtest'));

false
false

--- orig.js	2026-10-22 14:15:28.825129146 -0400
+++ fixed.js	2026-10-22 14:15:31.089191355 -0400
@@ -1,3 +1,3 @@
-const re = /=\u003D/u;
+const re = /[=]\u003D/u;
 console.log(re.test('=='));
 console.log('Match:', re.test('='));

true
Match: false

--- orig.js	2026-10-22 14:15:32.846239897 -0400
+++ fixed.js	2026-10-22 14:15:35.756320788 -0400
@@ -1,5 +1,5 @@
 "use strict";
 (function() {
-  const result = /=(.+)/.test('=value') ? RegExp.$1 : 'none';
+  const result = /[=](.+)/.test('=value') ? RegExp.$1 : 'none';
   console.log(result);
 })();

value

--- orig.js	2026-10-22 14:15:32.896241280 -0400
+++ fixed.js	2026-10-22 14:15:35.206305452 -0400
@@ -1,9 +1,9 @@
 const obj = {
   value: 42,
   check: function() {
-    return /=/.test(this.value.toString());
+    return /[=]/.test(this.value.toString());
   },
-  checkArrow: () => /=/.test(this.value.toString())
+  checkArrow: () => /[=]/.test(this.value.toString())
 };
 console.log(obj.check());
 console.log(obj.checkArrow());

false