diff --git a/packages/devextreme/js/__internal/core/utils/m_data.ts b/packages/devextreme/js/__internal/core/utils/m_data.ts
index fd2626f52fd5..c2be20be8331 100644
--- a/packages/devextreme/js/__internal/core/utils/m_data.ts
+++ b/packages/devextreme/js/__internal/core/utils/m_data.ts
@@ -13,12 +13,12 @@ const { assign } = variableWrapper;
 
 const bracketsToDots = function (expr) {
   return expr
-    .replace(/\[/g, '@js/core/utils')
+    .replace(/\[/g, '.')
     .replace(/\]/g, '');
 };
 
 export const getPathParts = function (name) {
-  return bracketsToDots(name).split('@js/core/utils');
+  return bracketsToDots(name).split('.');
 };
 
 const readPropValue = function (obj, propName, options) {
@@ -125,7 +125,7 @@ function combineGetters(getters) {
       }
 
       let current = result || (result = {});
-      const path = name.split('@js/core/utils');
+      const path = name.split('.');
       const last = path.length - 1;
 
       for (let i = 0; i < last; i++) {
diff --git a/packages/devextreme/js/__internal/core/utils/m_extend.ts b/packages/devextreme/js/__internal/core/utils/m_extend.ts
index 55f68d6277ba..09c454ddc6a8 100644
--- a/packages/devextreme/js/__internal/core/utils/m_extend.ts
+++ b/packages/devextreme/js/__internal/core/utils/m_extend.ts
@@ -2,26 +2,27 @@ import { isPlainObject } from '@js/core/utils/type';
 
 export const extendFromObject = function (target, source, overrideExistingValues) {
   target = target || {};
-  Object.keys(source).forEach((prop) => {
+  // eslint-disable-next-line no-restricted-syntax
+  for (const prop in source) {
     if (Object.prototype.hasOwnProperty.call(source, prop)) {
       const value = source[prop];
       if (!(prop in target) || overrideExistingValues) {
         target[prop] = value;
       }
     }
-  });
+  }
   return target;
 };
 
-export const extend = function (target, ...args: any[]) {
-  target = target || {};
+export const extend = function (...args) {
+  let target = args[0] || {};
 
-  let i = 0;
+  let i = 1;
   let deep = false;
 
   if (typeof target === 'boolean') {
     deep = target;
-    target = args[0] || {};
+    target = args[1] || {};
     i++;
   }
 
@@ -31,19 +32,20 @@ export const extend = function (target, ...args: any[]) {
       continue;
     }
 
-    Object.keys(source).forEach((key) => {
+    // eslint-disable-next-line no-restricted-syntax, guard-for-in
+    for (const key in source) {
       const targetValue = target[key];
       const sourceValue = source[key];
       let sourceValueIsArray = false;
       let clone;
 
       if (key === '__proto__' || key === 'constructor' || target === sourceValue) {
-        return;
+        continue;
       }
 
       if (deep && sourceValue && (isPlainObject(sourceValue)
-          // eslint-disable-next-line no-cond-assign
-          || (sourceValueIsArray = Array.isArray(sourceValue)))) {
+              // eslint-disable-next-line no-cond-assign
+              || (sourceValueIsArray = Array.isArray(sourceValue)))) {
         if (sourceValueIsArray) {
           clone = targetValue && Array.isArray(targetValue) ? targetValue : [];
         } else {
@@ -54,7 +56,7 @@ export const extend = function (target, ...args: any[]) {
       } else if (sourceValue !== undefined) {
         target[key] = sourceValue;
       }
-    });
+    }
   }
 
   return target;