diff --git a/packages/core-js/internals/ieee754.js b/packages/core-js/internals/ieee754.js
index ae1b9ffecdc4..057c4bd91bf9 100644
--- a/packages/core-js/internals/ieee754.js
+++ b/packages/core-js/internals/ieee754.js
@@ -54,7 +54,7 @@ var pack = function (number, mantissaLength, bytes) {
       exponent = eMax;
     } else if (exponent + eBias >= 1) {
       mantissa = roundToEven((number * c - 1) * pow(2, mantissaLength));
-      exponent = exponent + eBias;
+      exponent += eBias;
     } else {
       mantissa = roundToEven(number * pow(2, eBias - 1) * pow(2, mantissaLength));
       exponent = 0;
@@ -103,8 +103,8 @@ var unpack = function (buffer, mantissaLength) {
   } else if (exponent === eMax) {
     return mantissa ? NaN : s ? -Infinity : Infinity;
   } else {
-    mantissa = mantissa + pow(2, mantissaLength);
-    exponent = exponent - eBias;
+    mantissa += pow(2, mantissaLength);
+    exponent -= eBias;
   } return (s ? -1 : 1) * mantissa * pow(2, exponent - mantissaLength);
 };
 
diff --git a/packages/core-js/modules/es.regexp.constructor.js b/packages/core-js/modules/es.regexp.constructor.js
index 1f1ce0dc74aa..f922ed5b5555 100644
--- a/packages/core-js/modules/es.regexp.constructor.js
+++ b/packages/core-js/modules/es.regexp.constructor.js
@@ -86,7 +86,7 @@ var handleNCG = function (string) {
   for (; index <= length; index++) {
     chr = charAt(string, index);
     if (chr === '\\') {
-      chr = chr + charAt(string, ++index);
+      chr += charAt(string, ++index);
     } else if (chr === ']') {
       brackets = false;
     } else if (!brackets) switch (true) {
diff --git a/tests/eslint/eslint.config.js b/tests/eslint/eslint.config.js
index 234b4bd75e71..ef5650863b9b 100644
--- a/tests/eslint/eslint.config.js
+++ b/tests/eslint/eslint.config.js
@@ -260,6 +260,8 @@ const base = {
   'object-shorthand': ERROR,
   // require newlines around variable declarations with initializations
   'one-var-declaration-per-line': [ERROR, 'initializations'],
+  // require assignment operator shorthand where possible
+  'operator-assignment': [ERROR, 'always'],
   // require using arrow functions for callbacks
   'prefer-arrow-callback': ERROR,
   // require const declarations for variables that are never reassigned after declared