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;
})