JS计算元素屏幕居中
var scrollTop = $(document).scrollTop(); //滚动条高度
var clientHeight = document.documentElement.clientHeight; //屏幕的可见高度
var domHeight = 452; //元素的高度
var h = ((clientHeight - domHeight) / 2) + scrollTop;

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var scrollTop = $(document).scrollTop(); //滚动条高度
var clientHeight = document.documentElement.clientHeight; //屏幕的可见高度
var domHeight = 452; //元素的高度
var h = ((clientHeight - domHeight) / 2) + scrollTop;