🗒️页面是否激活

// 字段名，有浏览器兼容性问题（这里先忽略）
if (typeof document.hidden !== "undefined") {
    hidden = "hidden"
    visibilityChange = "visibilitychange"
    state = "visibilityState"
}

// 关键代码
document.addEventListener('visibilitychange', function() {
    // 'hidden', 'visible'
    $vm.tab_visibility = document['visibilityState']
    if($vm.tab_visibility == 'visible'){
        EventBus.$emit('pg_visible')
        socketIO.revisible()
    }else{
        socketIO.rehide()
    }
}, false)

window.addEventListener('online',  () => {
    EventBus.$emit('pg_visible')
})