Javascript - get a date from an HTML input

document.getElementById("dateInput").addEventListener("change", function() {
    var input = this.value;
    var dateEntered = new Date(input);
    console.log(input); //e.g. 2015-11-13
    console.log(dateEntered); //e.g. Fri Nov 13 2015 00:00:00 GMT+0000 (GMT Standard Time)
});

Basically you need to listen for the change of your date input, currently you were trying to get the value on load, when the picker has no date in it hence you get 'Invalid Date'