JSFiddle - React, Tailwind, and code Playground

JavaScript

var iDiv = document.createElement('div');
    iDiv.id = 'block';
    iDiv.className = 'block';
    document.getElementsByTagName('body')[0].appendChild(iDiv);
    iDiv.style.backgroundColor = "#d79365";
    iDiv.style.padding = "40px";

    var innerDiv2 = document.createElement('div');
    innerDiv2.className = 'block-3';

    iDiv.appendChild(innerDiv2);
    innerDiv2.style.padding = "40px";
    innerDiv2.style.textAlign = "center";
    innerDiv2.innerHTML = "Here is changing the text: ";
    //innerDiv2.innerHTML = "Text Change when button clicked";
    //innerDiv2.style.textAlign = "center";



    // Now create and append to iDiv
    var innerDiv = document.createElement('div');
    innerDiv.className = 'block-2';

    // The variable iDiv is still good... Just append to it.
    iDiv.appendChild(innerDiv);
    innerDiv.innerHTML = "I'm the inner div";
    innerDiv.style.padding = "40px";
    innerDiv.style.backgroundColor = "#eac67a";

    var ClickButton = document.createElement('button');
    ClickButton.id = 'btn';
    ClickButton.className = 'block-4';
    iDiv.appendChild(ClickButton);
    ClickButton.innerHTML = "Style";
    ClickButton.style.margin = "auto";
    ClickButton.style.display = "block";
    ClickButton.style.width = "80px";
    ClickButton.style.height = "50px";
    ClickButton.style.top = "50px";
    ClickButton.style.backgroundColor = "#233237";
    ClickButton.style.color = "white";

    function js_style(){
        alert("hi");
        document.querySelector("innerDiv2");
        innerDiv2.style.fontSize = 'large';
        innerDiv2.style.font = 'italic bold 20px arial,serif';
        innerDiv2.style.color = "#eac67a";
    };

    document.getElementById('btn').onclick = js_style;