监听浏览器各个标签间的切换
document.addEventListener('visibilitychange',function(e){
console.log(document.visibilityState);
let state = document.visibilityState
if(state == 'hidden'){
console.log(document.visibilityState,'用户离开了');
}
if(state == 'visible'){
console.log(document.visibilityState,'回来了');
}
})