JSFiddle - React, Tailwind, and code Playground

HTML

Year: <input id='txt1' type="text"/>
Week: <input id='txt2' type="text"/>

<input type="button" value="GET" onclick="GetDate()"/>
<span id="Day"></span>

JavaScript

function GetDate(){
var year = $('#txt1').val().trim();
var week = $('#txt2').val().trim();
var d = new Date(year, 0, 1);
var days = ['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'];
d.setDate(d.getDate() + (week * 7));    
$('#Day').text(days[d.getDay()]);
}