EloquentJavaScript: !Number.isNaN() what is the purpose? [duplicate]

This question already has an answer here:

• Is Number.IsNaN() more broken than isNaN() 6 answers

In Eloquent JavaScript rev.3 (http://eloquentjavascript.net/02_program_structure.html)there is a code snippet:

let theNumber = Number(prompt("Pick a number"));
if (!Number.isNaN(theNumber)) {
  console.log("Your number is the square root of " +
              theNumber * theNumber);
}

Here is what I understand:

First: create a variable and assign the window.prompt method to it. Use the Number wrapper object to convert the string to a number.

Second: Create a conditional and check if the the variable is NaN (not a number) If no (the ! operator), log the square root in the console.

What I don't understand is the meaning of !Number.isNaN... Why is the author doing it that way?

Isn't it enough to just write the condition as:

if (!isNaN(theNumber) {...}

Thanks in advance!