javascript - ResizeObserver 是否最初在页面加载时调用？

Question

似乎当我在 DOMContentLoaded 事件上将节点传递给 ResizeObserver.observe() 时，它会立即调用。它被认为是正常行为吗？

Answer 1

是的，此行为符合规范 (ref.):

• Observation will fire when watched Element is inserted/removed from DOM.

• Observation will fire when watched Element display gets set to none.

• Observations do not fire for non-replaced inline Elements.

• Observations will not be triggered by CSS transforms.

• Observation will fire when observation starts if Element is being rendered, and Element’s size is not 0,0.

因此，在您的情况下，要么该元素尚未在 DOM 中，要么情况 1 将使其触发，要么已经存在，而情况 5 将(尽管在 DOMContentLoaded 中，应该是 5 ;)。