How Do I Reliably Detect NaN Values After Using parseFloat() in JavaScript?

Determining NaN Values in JavaScript

When attempting to parse a non-numeric string as a number using JavaScript's parseFloat() function, it may not always return NaN as expected.

Problem:

In Firefox's JavaScript console, the following statements fail to return true:

parseFloat('geoff') == NaN;

parseFloat('geoff') == Number.NaN;

Solution:

To accurately check for NaN, use the isNaN() function:

isNaN(parseFloat("geoff"))

This code will return true because parseFloat("geoff") returns NaN.

Note:

The isNaN() function can also be used to test any value for NaN, not just numbers. For more details, refer to this guide: How do you test for NaN in JavaScript?

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