display date in javascript

var currentDateAndTime=new Date().toLocaleString(); //"8/5/2019, 2:30:41 PM"
var currentDate=new Date().toLocaleDateString(); //"8/5/2019"
var currentTime=   new Date().toLocaleTimeString();//"2:31:56 PM"

var date = new Date(); //Will use computers date by default.
//parameters will specify date you put to input
var date = new Date(year, month, day, hours, minutes, seconds, milliseconds);

var d = new Date(),
    minutes = d.getMinutes().toString().length == 1 ? '0'+d.getMinutes() : d.getMinutes(),
    hours = d.getHours().toString().length == 1 ? '0'+d.getHours() : d.getHours(),
    ampm = d.getHours() >= 12 ? 'pm' : 'am',
    months = ['Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec'],
    days = ['Sun','Mon','Tue','Wed','Thu','Fri','Sat'];
return days[d.getDay()]+' '+months[d.getMonth()]+' '+d.getDate()+' '+d.getFullYear()+' '+hours+':'+minutes+ampm;

let d = new Date();
console.log(d);

<button onclick="displayDate()">The time is?</button>

<script>
function displayDate() {
  document.getElementById("demo").innerHTML = Date();
}
</script>