how to detect screen size javascript code example

Example 1: get window resolution javascript

var clientWidth = document.documentElement.clientWidth;
 $("h2").text(clientWidth);

Example 2: js know size of screen

alert("Your screen resolution is: " + screen.width + "x" + screen.height)

Example 3: js detect screen size change

window.onresize = function(){
console.log("resize");
}