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Author: anitagupta1

web/src/pages/challenges/primitives.mdx

@@ -450,3 +450,42 @@ getDaysBetweenDates("10/15/2020", "12/1/2020"); // 47
 **References**
 
 - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date
+---
+
+### 19. How can you detect NaN in JavaScript?
+
+NaN is a special numeric value in JavaScript that indicates "Not-a-Number." You can use Number.isNaN() or isNaN() to check for NaN, though they behave differently.
+
+```javascript
+
+console.log(Number.isNaN(NaN));           // true
+console.log(Number.isNaN("hello"));       // false (doesn't coerce)
+console.log(Number.isNaN(undefined));     // false
+
+console.log(isNaN(NaN));                  // true
+console.log(isNaN("hello"));              // true (coerces to NaN)
+console.log(isNaN(undefined));            // true (coerces to NaN)
+```
+**References**
+
+- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isNaN
+---
+
+### 20. Show how to use Object.is for equality comparison between primitives
+
+Object.is can be used to check strict equality between two values, especially in edge cases like NaN, 0 and -0, where === may behave differently.
+
+```javascript
+
+console.log(Object.is(10, 10));               // true
+console.log(Object.is("hello", "hello"));     // true
+console.log(Object.is(NaN, NaN));             // true (different from ===)
+console.log(Object.is(0, -0));                // false (different from ===)
+console.log(Object.is(null, null));           // true
+console.log(Object.is(undefined, undefined)); // true
+console.log(Object.is(Symbol(), Symbol()));   // false (different symbols are unique)
+```
+**References**
+
+- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is
+---