docs: Use Object.defineProperty() for stubbing global propert… (#9288)

Author: vvanpo

docs/ManualMocks.md

@@ -141,8 +141,9 @@ If some code uses a method which JSDOM (the DOM implementation used by Jest) has
 In this case, mocking `matchMedia` in the test file should solve the issue:
 
 ```js
-window.matchMedia = jest.fn().mockImplementation(query => {
-  return {
+Object.defineProperty(window, 'matchMedia', {
+  writable: true,
+  value: jest.fn().mockImplementation(query => ({
     matches: false,
     media: query,
     onchange: null,
@@ -151,7 +152,7 @@ window.matchMedia = jest.fn().mockImplementation(query => {
     addEventListener: jest.fn(),
     removeEventListener: jest.fn(),
     dispatchEvent: jest.fn(),
-  };
+  })),
 });
 ```
 

website/versioned_docs/version-23.x/ManualMocks.md

@@ -142,8 +142,9 @@ If some code uses a method which JSDOM (the DOM implementation used by Jest) has
 In this case, mocking `matchMedia` in the test file should solve the issue:
 
 ```js
-window.matchMedia = jest.fn().mockImplementation(query => {
-  return {
+Object.defineProperty(window, 'matchMedia', {
+  writable: true,
+  value: jest.fn().mockImplementation(query => ({
     matches: false,
     media: query,
     onchange: null,
@@ -152,7 +153,7 @@ window.matchMedia = jest.fn().mockImplementation(query => {
     addEventListener: jest.fn(),
     removeEventListener: jest.fn(),
     dispatchEvent: jest.fn(),
-  };
+  })),
 });
 ```