JSFiddle - React, Tailwind, and code Playground

HTML

<span class="foo">bar</span>
<span class="foo">bar</span>

JavaScript

if (
    typeof document.getElementsByClassName !== 'function' &&
    typeof document.querySelectorAll === 'object'
){
    document.getElementsByClassName = function( name ){
        return document.querySelectorAll('.'+name);    
    }    
}    
        
console.log( document.getElementsByClassName('foo') );