Js The Weird Parts Guide

And arrow functions? They don’t have their own this at all—they inherit from the surrounding scope. Arrays in JS are just objects with numeric keys and a special length property. That means you can do... questionable things.

You are not alone. JavaScript is the quirky, misunderstood genius of the programming world. It was built in 10 days, it drives the modern web, and it has a list of "features" that look more like bugs. js the weird parts

If you’ve spent more than five minutes writing JavaScript, you’ve probably had a moment where you stared at your screen and whispered, “...why?” And arrow functions

const bound = showThis.bind("hello"); bound(); // String {"hello"} That means you can do

console.log(isNaN(NaN)); // true // But wait... console.log(isNaN("hello")); // true (because "hello" can't be a number) That’s why ES6 gave us Number.isNaN() which actually behaves. In many languages, if you forget to declare a variable, you get an error. In JavaScript (non-strict mode), you get a present :

function showThis() { console.log(this); } showThis(); // window (or undefined in strict mode)