Can you guess what will be the output of the code below?
console.log(typeof NaN);Show answer and explanation
typeof NaN actually returns "number", but why is that?
You can actually thank the IEEE Standard for Floating-Point Arithmetic (IEEE 754), which is the specification most programming languages base their implementation of floating point numbers on.
Imagine it this way:
Let’s use TypeScript here as an example to bring statical typing to JavaScript and imagine the following scenario:
const result: number = parseFloat(inputArgument);The code is pretty straight-forward. We want a number, and we have to parse an input argument for that.
But what if parseFloat actually cannot parse a float?
What if we forgot to validate the input and are now passing 'Does this work?' to parseFloat?
And this is where NaN comes into the game.
NaN simply states: “This is not a number”, but in a type-safe way, so you always get a result of type number.