JSFiddle - React, Tailwind, and code Playground

HTML

<table width="100%" border>
    <tr><td>1</td></tr>
    <tr><td>2</td></tr>
    <tr><td>3</td></tr>
    <tr><td>4</td></tr>
    <tr><td>5</td></tr>
    <tr><td>6</td></tr>
</table>

JavaScript

var tr = document.getElementsByTagName('tr');

for(i=0;i<tr.length;i++){
    if(i%2==0) 
    	tr[i].style.backgroundColor = 'red';
     else
      tr[i].style.backgroundColor = 'blue';
}