JSFiddle - React, Tailwind, and code Playground

HTML

<span class="test" />
<span class="test" />
<span class="test" />

CSS

.test
{
    color: #f80;
    font-weight: bold;
    padding: 4px;
    border: 2px solid #888;
}

.test:before
{
    content: "My Shiny New Product";
}

JavaScript

$(function() {
    
    //get all element class test
    var test = $('.test');
        
    //each of them, alert the content
    test.each(function() {
        var style = window.getComputedStyle(this, "before");
        alert(style.content);
    });
});