JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" name="startdate" value="2016-04-08">
<input type="text" name="enddate" value="2016-09-02">

JavaScript

var inputStart = document.querySelector('[name="startdate"]');
var inputEnd = document.querySelector('[name="enddate"]');

var startDate = getTimestamp(inputStart.value);
var endDate = getTimestamp(inputEnd.value);

console.log(endDate >= startDate);

function getTimestamp(dateString) {
	var arr = dateString.split('-');
  
  var date = new Date(
  	parseInt(arr[0], 10), 
    parseInt(arr[1], 10) - 1,
    parseInt(arr[2])
	);
 
 	return date.getTime();
}