get an html element
let h1 = document.querySelector("h1")
let = document.querySelector("#motorcycle") //this works if the element has the id 'motorcycle'
change its text
h1.innerText = "I have a secret message for you"
change an attribute
img.src = "motorcycle.png"
change its css
h1.style.color = 'green'
change a lot of its css
h1.style.cssText = "font-size: 100px; background-color:yellow"
add or remove a class
h1.classList.add('comicsans')
h1.classList.remove('comicsans')
change the css of the page
document.body.style.backgroundColor = "blue"
get a lot of html elements
let images = document.querySelectorAll("img")
change a lot of html elements
images.forEach(function(image){image.src = "mycoolimage.jpg"})
add html to page
document.body.innerHTML += ``
add html to element
h1.insertAdjacentHTML('beforeend', 'hahaha')
add html to beginning of element
h1.insertAdjacentHTML('afterbegin', "Narrator: ")
open a notification popup
alert("be careful!")
open a dialog box
confirm("would you like to continue?")
open popup window
window.open("https://www.youtube.com/watch?v=y6120QOlsfU", "sandstorm", "popup, left=100, top=100, width=600, height=300")