JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="mytext" />
<input type="button" id="myBtn" value="click" />

JavaScript

$("#myBtn").click(function() {
        var myInput = $("#mytext");
        myInput.val( myInput.val() + "()" );
        var pos = myInput.val().length - 1;
        myInput.focus();
        myInput[0].selectionStart = myInput[0].selectionEnd = pos;
    })