[英]UseEffect hook in next.js is causing 2 fetch requests when I expect 1, why?
The following code is causing 2 requests to be made to my API with the GET endpoint.以下代码导致使用 GET 端点向我的 API 发出 2 个请求。 I don't understand useEffect() enough to know where to start to debug, but I don't want to cause unneccessary strain on the services that these API endpoints will call server side.
我对 useEffect() 的了解还不足以知道从哪里开始调试,但我不想对这些 API 端点将调用服务器端的服务造成不必要的压力。 This is because they will be calling windows servers to action delete requests in active directory etc...
这是因为他们将调用 windows 服务器来处理活动目录中的删除请求等......
function Ad() {
const [data, setData] = useState(null)
const [isLoading, setLoading] = useState(false)
useEffect(() => {
setLoading(true)
fetch('../api/decom/ad')
.then(response => response.json())
.then(data => {
setData(data)
setLoading(false)
if (data.exists == true) {
Remove()
}
})
}, [])
const Remove = () => {
fetch("../api/decom/ad", { method: "DELETE" })
.then(response => response.json())
.then(data => {
var inner = ""
if (data.removed == true) {
inner = `<p>Removed: ${greenCircle}</p>`
} else {
inner = `<p>Removed: ${redCircle}</p>`
}
document.getElementById('adremoved').innerHTML = inner
})
}
if (data != null && data.exists == true) return (
<a className={styles.card}>
<h2>AD</h2>
<p>Exists: { greenCircle } </p>
<div id ="adremoved" className={styles.parent}>
<p className={styles.child}>removed:</p>
<div><div className={styles.loader}><div></div><div></div><div></div></div></div>
</div>
</a>
)
if (data != null && data.exists == false) return (
<a className={styles.card}>
<h2>AD</h2>
<p>Exists: {redCircle} </p>
<p>Removed:{redCircle}</p>
</a>
)
if (isLoading) return (
<a className={styles.card}>
<h2>AD</h2>
<div className={styles.parent}>
<p id="adstatus" name="adstatus" className={styles.child}>Exists:</p>
<div id="adloader"><div className={styles.loader}><div></div><div></div><div></div></div></div>
</div>
<p>Removed:{redCircle}</p>
</a>
)
}
const [isLoading, setLoading] = useState(true)
useEffect(() => {
if(isLoading){
fetch('../api/decom/ad')
.then(response => response.json())
.then(data => {
if (data.exists == true) {
Remove()
}else{
setData(data)
}
setLoading(false)
})
}
}, [isLoading])
If you are using react 18, useEffect hook will run twice, that is the expected behaviour如果您使用的是 React 18,useEffect 钩子将运行两次,这是预期的行为
React 18 introduces a new development-only check to Strict Mode. This new check will automatically unmount and remount every component, whenever a component mounts for the first time, restoring the previous state on the second mount.
https://reactjs.org/docs/strict-mode.html#ensuring-reusable-state https://reactjs.org/docs/strict-mode.html#ensuring-reusable-state
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