H5移动端，ios从后台返回到app，页面会白一下

visibilitychange事件可以检查从后台返回事件，然后通过添加div，强制浏览器刷新页面

var divEle = document.createElement("DIV");
        divEle.style.position = "absolute";
        divEle.style.left = "0px";
        divEle.style.top = "0px";
        divEle.style.width = "100%";
        divEle.style.height = "100%";
        divEle.style.zIndex = "9999999";
        divEle.style.backgroundColor = "#000";
        
        document.addEventListener("visibilitychange", () => {
            try {
                if (document.hidden) {
                    document.body.appendChild(divEle);
                }
                else {
                    document.body.removeChild(divEle);
                }
            }
            catch (e) {

            }
        });