A small sample implementation
javscript
appVar1 - is the app variable name which I linked to text filed …so on change of text the value changes
App.onVariableChange('appVar1', value => {
document.getElementById("abc").innerText = value;
});
HTML
<div id='abc' class="textContainer">
This is the HTML control content
</div>
How it works
Hope this helps
cheers