CSS in Javascript
<div class="Hello">
  <h1>grab me!</h1>
</div>
const h1 = document.querySelector(".hello h1")
fucntion handleTitleClick(){
  	const currentColor = h1.style.color;
  	let newColor;
  	if(currentColor === "blue"){
    	newColor = "tomato";
    }else{
    	newColor = "blue"
    }
  h1.style.color = newColor;
}
h1.addEventListner("click", handleTitClick)
body{
	background-color:beige;
}
h1{
	color:cornflowerblue;
    transition: color 0.5s ease-in-out
}
.clicked{
	color:tomato;
    
}
const h1 = document.querySelector(".hello h1")
/*fucntion handleTitleClick(){
  const clickedClass = "clicked";
  if(h1.className === clickedClass){
  	h1.className ="";
  }else{
  	h1.className = clickedClass;
  }
}*/
/*fucntion handleTitleClick(){
  const clickedClass = "clicked";
  if(h1.classList.contains(clickedClass)){
  	h1.classList.remove(clickedClass)
  }else{
  	h1.classList.add(clickedClass)
  }
}*/
fucntion handleTitleClick(){
  h1.classList.toggle("clicked");
}
h1.addEventListner("click", handleTitClick)
코딩챌린지
const bg = document.querySelector("body");
const title = document.querySelector("h1");
function handleResize() {
  let bgSize = window.innerWidth;
  if (bgSize >= 800) {
    title.classList.add("active");
    bg.style.backgroundColor = "yellow";
  } else if (bgSize < 800 && bgSize >= 600) {
    title.classList.add("active");
    bg.style.backgroundColor = "purple";
  } else {
    title.classList.add("active");
    bg.style.backgroundColor = "skyblue";
  }
}
window.addEventListener("resize", handleResize);