Make it clearer how to run an effect only once (componentDidMount style)

Based on this conversation on Twitter, it's perhaps not clear enough how to make an effect hook only run once on mount (a la componentDidMount.)

The relevant info on how to do it properly is tucked away near the bottom of the effect hook doc, in a footnote of this tip. This is a major use case that should probably have higher priority in the documentation. I imagine a vast majority of apps actually need to do use an effect in this manner.

I assume people are probably doing something like

function MyComponent({ fetchData, data }) {
  useEffect(() => {
    if (!data) {
      fetchData()
    }
  })
}

I can make the change to the docs, but where's the best place to put it? Should I make it a tip? Does it deserve higher priority than that?

從 effect hook 文件及其中的「提示：透過跳過 Effect 最佳化效能」部分開始，目前只在 mount 時執行一次的指引被隱藏在這裡。判斷 useEffect-on-mount 範例是否應放在優先順序更高的部分或提示中，然後確認文件清楚地說明了預期的模式。