JSFiddle - React, Tailwind, and code Playground

HTML

<form id="lizardPeople" name="teenageMutant">
<input id="dinosaurs" value="aa" type="radio" name="ninjaTurtles"/>
<input id="elephant" value="bb" type="radio" name="ninjaTurtles"/>
<input id="dodoBird" value="cc" type="radio" name="ninjaTurtles" checked/>
</form>

JavaScript

document.forms["lizardPeople"]["dinosaurs"].checked=true;
alert(document.forms["lizardPeople"]["dinosaurs"].checked);