JSFiddle - React, Tailwind, and code Playground
HTML
<input type="text" id="startDate" onchange="add7Days(this)" />
<input type="text" id="endDate" />
JavaScript
function formatDate(dat) {
return ('0' + (dat.getMonth() + 1)).slice(-2) + "/" + ('0' + dat.getDate()).slice(-2) + "/" + dat.getFullYear();
}
var startDate = new Date();
var startFormatedDate = formatDate(startDate);
// Assign start to end
var endDate = startDate;
endDate.setDate(endDate.getDate() + 7);
var endFormatedDate = formatDate(endDate);
document.getElementById('startDate').value = startFormatedDate;
document.getElementById('endDate').value = endFormatedDate;
function add7Days(d) {
var arr = d.value.split("/");
var reformat = new Date(arr[2], +(arr[0]) - 1, arr[1]);
reformat.setDate(reformat.getDate() + 7);
document.getElementById('endDate').value = formatDate(reformat);
}