在Firebase中使用onUpdate函数时，如何检索已更新的记录? [英] When using the onUpdate function in Firebase, how do I retrieve the record that has been updated?

问题描述

在Firebase上使用云功能时，通过onUpdate触发器，我如何检索已更新的记录(换句话说，触发该功能的记录)?我正在使用JavaScript与Firebase数据库进行交互.

When using the cloud functions on firebase, with the onUpdate trigger, how do I retrieve the record that has been updated (in other words, the record that triggers the function)? I am using JavaScript to interface with the Firebase database.

推荐答案

第一个参数通过了 onUpdate 处理函数是更改对象.此对象具有两个属性，之前和之后，均为 DataSnapshot 对象.这些DataSnapshot对象描述了触发函数的更改前后的数据库内容.

The first argument passed your onUpdate handler function is a Change object. This object has two properties, before and after, both DataSnapshot objects. These DataSnapshot objects describe the contents of the database before and after the change that triggered the function.

exports.foo = functions.database.ref('/location-of-interest')
.onUpdate((change) => {
    const before = change.before  // DataSnapshot before the change
    const after = change.after  // DataSnapshot after the change
})

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