我正在嘗試使用 JavaScript 將海報 URL 添加到我的 neo4j 電影數據庫，但我一直收到此未定義對象錯誤

Question

我對 JavaScript 完全陌生，並且很難理解異步調用。 我是否需要嵌套另一個承諾對象來設置海報 URL？

async function getIds() {
    const result = await session.run("MATCH (m :Movie) RETURN m.imdbId LIMIT 5");
    const ids = [];
    result.records.forEach(record => ids.push(record._fields[0]));
    return ids;
}

async function imdbIds() {
    const ids = await getIds();
    console.log(ids);
    const response = await Promise.all(ids.map(async id => {
        // webscraper that returns poster url of each imdbid
        const url = toString(scraper(id));
        console.log(url);

        // query to set poster of each id in neo4j db
        const result = await session.run("MATCH (m :Movie {imdbId : $id}) SET m.poster = $url RETURN m.poster", { id, url });
        result.records.forEach(record => console.log(record._fields[0]));
        return result;
    }));
    console.log(response);
}

imdbIds();

控制台日志仍然沒有運氣：

[ '0114709', '0113497', '0113228', '0114885', '0113041' ]
[object Undefined]
[object Undefined]
[object Undefined]
[object Undefined]
[object Undefined]
[object Undefined]
[object Undefined]
[object Undefined]
[object Undefined]
[object Undefined]
[ { records: [ [Record] ],
    summary:
     ResultSummary {
       statement: [Object],
       statementType: 'rw',
       counters: [StatementStatistics],
       updateStatistics: [StatementStatistics],
       plan: false,
       profile: false,
       notifications: [],
       server: [ServerInfo],
       resultConsumedAfter: [Integer],
       resultAvailableAfter: [Integer] } } ...

Answer 1

問題是你的getIds函數。 你已經在另一個承諾中包裝了一個已經承諾的返回函數。 第二個問題是你的 getIds 函數。 您正在 forEach 中進行異步操作，這將不起作用。 Promise.all應該是這樣的

async function getIds() {
  const result = await session.run("MATCH (m :Movie) RETURN m.imdbId LIMIT 5");
  const ids = [];
  result.records.forEach(record => ids.push(record._fields[0]));
  return ids;
}

async function imdbIds() {
  const ids = await getIds();
  console.log(ids);
  const response = await Promise.all(ids.map(async id => {
    // webscraper that returns poster url of each imdbid
    const url = toString(scraper(id));
    console.log(url);

    // query to set poster of each id in neo4j db
    const result = await session.run("MATCH (m :Movie {imdbId : $id}) SET m.poster = $url RETURN m.poster", {id, url});
    result.records.forEach(record => console.log(record._fields[0]));
    return result;
  }));
  console.log(response);
}

Answer 2

想通了，感謝先生的幫助。 阿什莫迪

async function setPosters() {
    const result = await session.run("MATCH (m :Movie) RETURN m.imdbId LIMIT 15");
    result.records.forEach(async record => {
        const imdbId = record._fields[0];
        const url = await scraper(imdbId);
        await session.run("MATCH (m :Movie {imdbId : $imdbId}) SET m.poster = $url RETURN m.poster", { imdbId, url });
    });
}

setPosters();