TypeError：無法讀取null MongoDb錯誤的屬性“長度”

Question

在查詢中獲取mongodb錯誤。 這里的錯誤：

TypeError：無法讀取null的屬性“ length”

這是代碼：

// Open a connection with MongoDB

MongoClient.connect(process.env.MONGO_URL, (error, db) => {
  let dbo = db.db('gamblenomore');

//Running a query to find all customers that are in timezone CST.

dbo.collection('customers').find({therapyConfirmation: true, therapyTimeZone: 'CST', therapyDay: { $gt: 0 } }).toArray((error, result) => {
    let max = result.length;
    if (error) {
      throw error;
    }

'customers'當前沒有符合上述條件的文件。

Answer 1

將您的代碼更改為：

dbo.collection('customers').find({
  therapyConfirmation: true,
  therapyTimeZone: 'CST', 
  therapyDay: { $gt: 0 } 
}).toArray((error, result) => {
    if (error) {
      throw error;
    }
    let max = result.length;
    // some other code
});