Question

我在使用nodejs和mongoose的代码中遇到问题。我有一个应该从mongodb（book.findOne）获取书籍的函数，然后使用第二个查询（updateMany）更新它们。问题是UpdateMany查询在获取书籍之前执行..所以我的数组保持为空并且没有任何更新。我知道node.js是异步的，但我怎么能解决这个问题？

function UpdateBulk(completeValidBooks){
    var existingRowsInDb = [];
    completeValidBooks.forEach(function(currentBook) {

           book.findOne({'ISIN':  currentBook.ISIN }, 
            function(error, result) {
              existingRowsInDb.push(result);             
            });
          });


        book.updateMany(existingRowsInDb, (err,docs) => {
          err ? console.log(err) : console.log(`updated ${docs.length}`);

          });



}

Answer 1

使用诺言你可以这样做：

function UpdateBulk(completeValidBooks) {
  GetExistingRows(completeValidBooks).then((existingRowsInDb) => {
    book.updateMany(existingRowsInDb, (err, docs) => {
      err ? console.log(err) : console.log(`updated ${docs.length}`);
    });
  })
}

function GetExistingRows(completeValidBooks) {
  return new Promise((resolve, reject) => {
    var existingRowsInDb = [];
    completeValidBooks.forEach((currentBook) => {
      book.findOne({
        'ISIN': currentBook.ISIN
      }, (error, result) => {
        existingRowsInDb.push(result);
      });
    });
    resolve(existingRowsInDb);
  })
}

使用回调你可以这样做：

function UpdateBulk(completeValidBooks) {
  GetExistingRows(completeValidBooks, (existingRowsInDb) => {
    book.updateMany(existingRowsInDb, (err, docs) => {
      err ? console.log(err) : console.log(`updated ${docs.length}`);
    });
  })
}

function GetExistingRows(completeValidBooks, callback) {
  var existingRowsInDb = [];
  completeValidBooks.forEach((currentBook) => {
    book.findOne({
      'ISIN': currentBook.ISIN
    }, (error, result) => {
      existingRowsInDb.push(result);
    });
  });
  callback(existingRowsInDb);
}

mongoose查询执行顺序

1 个答案: