Changes how we use querySelector, querySelectorAll, addEventListener, and removeEventListener.

app.js

// # Changes how we use querySelector, querySelectorAll, addEventListener, and removeEventListener.
const $ = () => document.querySelector.call(this, arguments);
const $$ = () => document.querySelectorAll.call(this, arguments);
HTMLElement.prototype.on = (a, b, c) => this.addEventListener(a, b, c);
HTMLElement.prototype.off = (a, b) => this.removeEventListener(a, b);

// And therefore we can use this like...
let nav = $("nav");
// rather than...
let nav = document.querySelector("nav");