5.screen对象

screen对象包含有关客户端显示屏幕的信息
screen.availWidth
screen.availHeight

// 获取屏幕的宽度
var screenWidth = window.screen.availWidth;
console.log(screenWidth);
// 获取屏幕的可视区
var viewWidth = document.body.clientWidth;
console.log(viewWidth);