JS getElement

 

//head- script - window.onload=function 내부
 
let e1=document.getElementById("t1");
let e2=document.getElementsByClassName("a");
let e3=document.getElementsByTagName("div");
  /* id로 읽어오는것은 1개씩..
     className, TagName으로 가져오는것은 '배열' */
 
 
//body
<div id="t1" class="a">hello</div>
<div class="a">hello2</div>
<div>hello3</div>
 
//get element로 
window.onload=function(){
    document.getElementById("a1").style.backgroundColor="aqua";
    var d =document.getElementsByTagName("div");
    for(let i = 0;i <d.length; i++){
        if(i%2==0){ //짝수만 color 변경
            d[i].style.color="green";
        }
    }
}