英文:
Firebase update function performs recursively
问题
这是你提供的代码的翻译部分：
function like(id) {
firebase.database().ref("memes/" + id).on("value", (snap) => {
const cs = snap.val().likes || [{
name: ""
}];
let res = [...cs, JSON.parse(localStorage.getItem("user"))].filter(item => item);
console.log(res);
firebase.database().ref("memes/" + id).update({
likes: res,
});
});
}
<p><button onclick="like('${y.name}/${y.head}')"><ion-icon name="thumbs-up"></ion-icon></button><b>${1 || y.likes.length }</b></p>
问题是，当我点击按钮时，like函数会递归执行，不断在RealTime数据库中的likes字段（一个数组）中添加对象。
就像这样：
likes:
0-> object
1-> object
....
英文:
I am making a website of where people can upload memes but I'm currently stuck at updating likes of meme
Here's the code
Js
function like(id) {
firebase.database().ref("memes/" + id).on("value", (snap) => {
const cs = snap.val().likes || [{
name: ""
}]
let res = [...cs, JSON.parse(localStorage.getItem("user"))].filter(item => item)
console.log(res)
firebase.database().ref("memes/" + id).update({
likes: res,
});
})
}
html
<p><button onclick="like('${y.name}/${y.head}')"><ion-icon name="thumbs-up"></ion-icon></button><b>${1 || y.likes.length }</b></p>
Problem is when I click on button the like function performs like recursively and just keeps adding objects in like field which is array in RealTime database .
Like this:
likes:
0-> object
1-> object
....
答案1
得分: 1
你正在使用以下代码打开一个监听器来监听 memes/{id}/：
firebase.database().ref("memes/" + id).on("value",(snap) => {
所以每次更新时，你都会得到另一个回调，这就是为什么它不断递归添加项目。
你可以将其替换为 once，这应该解决你的问题。
参考链接：https://firebase.google.com/docs/database/admin/retrieve-data#section-reading-once
关于 on value 的解释：
https://firebase.google.com/docs/database/admin/retrieve-data#value
value事件用于读取给定数据库路径上的内容的静态快照，这些内容在读事件发生时存在。它在初始数据上触发一次，然后在数据更改时再次触发。
英文:
You are opening a listener to memes/{id}/ with the code:
firebase.database().ref("memes/" + id).on("value",(snap) => {
So every time you update you get another callback and that's why it keeps recursivelly adding items.
You can replace it with once and that should solve your problem.
Reference: https://firebase.google.com/docs/database/admin/retrieve-data#section-reading-once
Explanation for the on value:
https://firebase.google.com/docs/database/admin/retrieve-data#value
> The value event is used to read a static snapshot of the contents at a given database path, as they existed at the time of the read event. It is triggered once with the initial data and again every time the data changes.
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