fix(curriculum): step 89 hasOwnProperty fix (freeCodeCamp#55791)

Co-authored-by: Jessica Wilkins <[email protected]>

Author: gagan-bhullar-tech

curriculum/challenges/english/15-javascript-algorithms-and-data-structures-22/learn-functional-programming-by-building-a-spreadsheet/646d4626420eeecd51f241c2.md

@@ -11,6 +11,22 @@ Update the callback function to take `match`, `fn`, and `args` as parameters. It
 
 Remember to make `fn` lower case.
 
+To check if a property on a given object exists or not, you can use the <dfn>hasOwnProperty()</dfn> method. 
+
+The `hasOwnProperty()` method returns `true` or `false` depending on if the property is found on the object or not.
+
+Here is an example of how to use the `hasOwnProperty()` method:
+
+```js
+const developerObj = {
+  name: 'John',
+  age: 34,
+}
+
+developerObj.hasOwnProperty('name'); // true
+developerObj.hasOwnProperty('salary'); // false
+```
+
 # --hints--
 
 Your callback function should have `match` as the first parameter.