JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">data</div>

JavaScript

var container = document.getElementById('container');

function block(mClass, html) {
    //extra html you want to store.
    return '<div class="' + mClass + '">' + html + '</div>';
}

//    code that loops and makes the blocks.
//    first part: creates var i
//    second:     condition, if 'i' is still smaller than three, then loop.
//    third part: increment i by 1;
for (var i = 0; i < 3; i++) {
    // append the result of function 'block()' to the innerHTML
    // of the container.
    container.innerHTML += block('block', 'data');
}