JavaScript NaN Function

The JavaScript NaN (Not-a-Number) value is a special value that represents an invalid or unrepresentable numeric result. It is typically returned when a mathematical operation or function fails to produce a valid numeric result.

JavaScript provides several functions to check if a value is NaN or perform operations related to NaN. Here are a few commonly used functions:

1. isNaN(value): The isNaN() function checks if a value is NaN. It returns true if the value is NaN, and false otherwise. However, isNaN() has a quirk: it coerces the value to a number before performing the check. This means that non-numeric values are first converted to a number and then checked if they are NaN. This can lead to unexpected results, especially with non-numeric strings. To mitigate this, you can use Number.isNaN() (introduced in ES6) which performs a strict NaN check without type coercion. Example:

 isNaN(10); // Output: false
 isNaN("hello"); // Output: true
 isNaN("123"); // Output: false
 Number.isNaN("hello"); // Output: false
 Number.isNaN(NaN); // Output: true

2. isNaN() vs Number.isNaN(): As mentioned earlier, isNaN() performs type coercion before the check, while Number.isNaN() does not. It is generally recommended to use Number.isNaN() when specifically checking for NaN and use isNaN() when you want to check if a value cannot be converted to a number.
3. Object.is(value1, value2): The Object.is() function can also be used to check if a value is NaN. It performs a strict equality comparison, which means it checks if the values are identical, including NaN. Example:

 Object.is(NaN, NaN); // Output: true
 Object.is(10, NaN); // Output: false

These functions can be helpful when working with numeric calculations and handling situations where NaN values may occur. It’s important to use them appropriately based on your specific use case to ensure accurate results.