JSFiddle - React, Tailwind, and code Playground

HTML

<form>
    <p class="instructions">I need my items by:</p>
    <input type="date" name="date" value="" id="date" />
    <input type="button" value="Submit">
</form>
<p>Be sure to order by:</p>
<p id="dateoutput"></p>

JavaScript

document.getElementsByName("submit").onclick = function () {
        var dateIn = document.getElementsById("date").value;
        var addDays = 10;
        var dateOut = dateIn + addDays;
    };

    document.getElementById("dateoutput").innerHTML = dateOut;