檢測瀏覽器窗口最小化的兩種方法：
1.利用window的屬性
function isMinStatus() {
var isMin = false;
if (window.outerWidth != undefined) {
isMin = window.outerWidth <= 160 && window.outerHeight <= 28;
}
else {
isMin = window.screenTop < -30000 && window.screenLeft < -30000;
}
return isMin;
}
2.利用document的visibilityState和hidden屬性（推薦）
document.addEventListener("visibilitychange", function() {
console.log( document.visibilityState );
console.log( document.hidden);
});