内容参考github ts问题11085
DomRect之前叫ClientRect,后来更名了1,
ts兼容了两种对象,但ClientRect没有x,y属性。所以使用getBoundingClientRect时:
let unspecifiedRect = document.body.getBoundingClientRect();
unspecifiedRect.x // fails
let domRect = document.body.getBoundingClientRect() as DOMRect;
domRect.x // works