Thread by @swapnakpanda

💙 NaN in JavaScript

Operations evaluating to NaN
↳ Conversion to a Number
↳ Parsing to a Number
↳ Indeterminate Forms
↳ Math functions

Let's explore.

⇩

1️⃣ Conversion to a Number

Conversion happens in 2 ways in JavaScript

↳ Implicit Conversion
Operations where a number is expected
Example: Unary +, Binary - etc
↳ Explicit Conversion
Using Number() or, new Number()

Let's see what are evaluated to NaN

2️⃣ Parsing to a Number

There are 2 number parsing methods

↳ parseInt
↳ parseFloat

The process is,

✪ Leading and trailing spaces are ignored
✪ If the first character cannot be converted to a number, NaN is returned
✪ Only the first number found is returned

3️⃣ Indeterminate Forms

Some indeterminate forms which evaluate to NaN are,

⇰ 0 / 0
⇰ 0 % 0
⇰ 0 * Infinity
⇰ Infinity - Infinity
⇰ -Infinity + Infinity
⇰ Infinity / Infinity
⇰ Infinity % Infinity
⇰ Infinity % 0

4️⃣ Math functions

If invalid arguments are passed to Math functions, they may return NaN.

Example:

✪ Square root of a negative number
Math.pow(-2, 1/2)

✪ Logarithm of a negative number
Math.log2(-2)