我正在尝试使用 JavaScript 将海报 URL 添加到我的 neo4j 电影数据库，但我一直收到此未定义对象错误

Question

I'm completely new to JavaScript and having a hard time trying to understand asynchronous calls. Do I need to nest another promise object to set the poster URLs?

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();

Console logs still no luck:

[ '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

The problem is your getIds function. you have wrapped a already promise returning function in another promise. second problem is your getIds function. you are doing asynchronous operation in forEach which will not work. Replace it with Promise.all it should be like this

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

figured it out, thanks for help mr. ashish modi

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();