Page 163 - JavaScript

Chapter 17: Built-in Constants

Examples

Operations that return NaN

Mathematical operations on values other than numbers return NaN.

"a" + 1
"b" * 3
"cde" - "e"
[1, 2, 3] * 2

An exception: Single-number arrays.

[2] * [3] // Returns 6

Also, remember that the + operator concatenates strings.

"a" + "b" // Returns "ab"

Dividing zero by zero returns NaN.

0 / 0 // NaN

Note: In mathematics generally (unlike in JavaScript programming), dividing by zero is not
possible.

Math library functions that return NaN

Generally, Math functions that are given non-numeric arguments will return NaN.

Math.floor("a")

The square root of a negative number returns NaN, because Math.sqrt does not support imaginary
or complex numbers.

Math.sqrt(-1)

Testing for NaN using isNaN()

window.isNaN()

The global function isNaN() can be used to check if a certain value or expression evaluates to NaN.
This function (in short) first checks if the value is a number, if not tries to convert it (*), and then

https://riptutorial.com/ 120