static void

Document ready

$(document).ready(function () {
        //document is ready
}
//and
$(function(){
   //document is ready
 });

document.addEventListener("DOMContentLoaded", function(){
  //
});

//by id
$('#myId').onclick(function(e) {});
//by class
$('.myClass').hide();

//by id
document.getElementById('myId').addEventListener("click", function() {});
document.querySelector('#myId'); //also works
//by class - first only
document.querySelector('.myClass');
//by class - nodeList
var list = document.querySelectorAll('.myClass');
for ( var i = 0, var len = list.length; i < len; i++ ) {
    console.log(list[i]);
}
//pseudo selectors - find which radio checked
var value = document.querySelector('input[name="pick"]:checked').value;

//classes
$('#id').addClass('red');
$('#id').removeClass('green');
$('#id').toggleClass('yellow');

//IE10+
document.querySelector('#myId').classList.add('red');
document.querySelector('#myId').classList.remove('green');
document.querySelector('#myId').classList.toggle('yellow');

//events can be added to a group
$('.allButtons').onclick(function(e) {});

//add events individually (or parent)
document.querySelector('#myId').addEventListener('click', function(e) {});
//or parent
var ehandler= function(e) {
	var target = event.target;
	if (target.hasAttribute('x')) {
		e.preventDefault();
		//do something
	}
};
document.addEventListener('click', ehandler);

//using XMLHttpRequest
$.ajax({
	url: "/Notifications",
	method:"POST",
	data: JSON.stringify({ href: location.href}),
	contentType: "application/json; charset=utf-8",
	success: function (data) {
		console.log(data.Count.length);
	},
	error: function (e, textStatus, errorThrown) {
		//500 etc
		console.log(e.status + " status text=" + 
			e.statusText + " error=" + errorThrown);
	}
});

fetch("/Notifications",
		{
			method: 'POST',
			mode: 'cors',
			credentials: 'include', //by default it doesn't send auth cookies... 
			headers: {
				'Content-Type': 'application/json'
			},
			body: JSON.stringify({ href: location.href }) //matching header
		})
	//returns a response stream, so turn it into .json()
	.then((response) => {
		if (!response.ok) {
			throw new Error(response.url + 
				" returned " + response.status);
		}
		 return response.json();
	})
	.then((json) => {
		console.log(json.Count.length);
	})
	.catch ((e) => {
		console.log(e.message);
	});

NOT any version of IE!

MDN