JavaScript is weird!

JavaScript is the only language where your brain melts in seconds.

So yesterday, I’m building some app, right? I’m checking types, doing calculations… and then I see this:

console.log(typeof NaN); // "number"

WTF JavaScript. NaN = Not a Number. Type = “number”? My brain just did a flip. How does this make sense?!

Then I try something else:

let a;
console.log(a + 2); // NaN
console.log(a); // undefined

Okay, so undefined + 2 = NaN. Makes sense… kinda. But typeof a is “undefined”. Sure, okay. But NaN is number? My brain just filed for early retirement.

I spend the next 20 minutes testing stuff:

console.log(null == undefined); // true
console.log(null === undefined); // false
console.log([] + []); // ""
console.log([] + {}); // "[object Object]"
console.log({} + []); // 0 ????

WHAT?! Why does JS do this to me? Why is [] + {} a string but {} + [] = 0???

At this point, I unlocked a new mental badge:

“JavaScript Survivor” — For staring at the console like it personally betrayed you.

Seriously, JS is fun… until it isn’t. But you still love it, because no other language would let typeof(NaN) === "number" and let you survive it.