如何在Firebase上自动删除邮件

Question

我是Firebase Cloud Functions的新手。 一定时间后，如何在实时数据库中自动删除消息？例如1分钟1天，等等。

我正在尝试使用此处提供的示例（https://github.com/firebase/functions-samples/tree/master/delete-old-child-nodes），并在使用firebase deploy命令后收到以下错误：

i deploying functions Running command: npm --prefix "$RESOURCE_DIR" run lint

functions@ lint /home/vitor/remove_msgs_teste/functions eslint .

/home/vitor/remove_msgs_teste/functions/index.js 29:111 error Parsing error: Unexpected token =>

✖ 1 problem (1 error, 0 warnings)

npm ERR! code ELIFECYCLE npm ERR! errno 1 npm ERR! functions@ lint: eslint . npm ERR! Exit status 1 npm ERR! npm ERR! Failed at the functions@ lint script. npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in: npm ERR! /home/vitor/.npm/_logs/2019-04-15T12_51_56_231Z-debug.log

Error: functions predeploy error: Command terminated with non-zero exit code1

我的index.js：

'use strict';

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

// Cut off time. Child nodes older than this will be deleted.
const CUT_OFF_TIME = 30000; // 30sec in milliseconds.

/**
 * This database triggered function will check for child nodes that are older than the
 * cut-off time. Each child needs to have a `timestamp` attribute.
 */
exports.deleteOldItems = functions.database.ref('/mensagens/{idone}/{idtwo}/{pushid}').onWrite(async (change) => {
  const ref = change.after.ref.parent; // reference to the parent
  const now = Date.now();
  const cutoff = now - CUT_OFF_TIME;
  const oldItemsQuery = ref.orderByChild('timestamp').endAt(cutoff);
  const snapshot = await oldItemsQuery.once('value');
  // create a map with all children that need to be removed
  const updates = {};
  snapshot.forEach(child => {
    updates[child.key] = null;
  });
  // execute all updates in one go and return the result to end the function
  return ref.update(updates);
});

我的数据库：

如何解决此错误？

Answer 1

您似乎正在尝试将需要节点8的代码（因为它使用=>表示法）部署到不支持它的环境中。

解决方案是升级环境以支持节点8。另一种方法是修改代码以不再需要节点8，可以通过以下方式完成：

exports.deleteOldItems = functions.database.ref('/mensagens/{idone}/{idtwo}/{pushid}').onWrite(function(change) {
  var ref = change.after.ref.parent; // reference to the parent
  var now = Date.now();
  var cutoff = now - CUT_OFF_TIME;
  var oldItemsQuery = ref.orderByChild('timestamp').endAt(cutoff);
  return oldItemsQuery.once('value').then(function(snapshot) {
    // create a map with all children that need to be removed
    var updates = {};
    snapshot.forEach(function(child) {
      updates[child.key] = null;
    });
    // execute all updates in one go and return the result to end the function
    return ref.update(updates);
  });
});

---

这种类型的重写在现代JavaScript中相当普遍，因此我认为您是新手。如果您不熟悉JavaScript，则Firebase Cloud Functions不是学习它的最佳方法。我建议先阅读Firebase documentation for Web developers和/或参加Firebase codelab for Web developer。它们涵盖了许多基本的JavaScript，Web和Firebase交互。您还可以在本地Node.js进程中使用Admin SDK，可以使用本地调试器对其进行调试。在那之后，您也将更有能力为Cloud Functions编写代码。