JSFiddle - React, Tailwind, and code Playground

by mbutubuntu

HTML

<div class='aa'></div>
<div class='aa'></div>
<div class='aa'></div>
<div class='aa'></div>
<div class='bb'>click here</div>

CSS

.aa{
 position: relative;
 float: left;
 width: 300px;
 height: 20px;
 background: black;    
}

.bb{
 position: relative;
 float: left;
 width: 300px;
 height: 20px;
 background: red;       
}

JavaScript

function getElementsByClassName(sel){
    var a = document.getElementsByTagName("*");
    var o = [];
    for(var i = a.length-1; i>=0; i--){
        var cl = a[i].className;
        if(cl.split(" ").indexOf(sel) !== -1){
             o.push(a[i]);
        }
    }
    return o;
}


function change(){
var a = getElementsByClassName("aa");
for(var i = a.length-1; i>=0; i--){
    var st = a[i].style;
    st.background = "blue";       
}
}

getElementsByClassName("bb")[0].onclick = change;