await function Anahtar Kelimesi

Giriş
async metodun bitmesini bekler.

Örnek

Elimizde şöyle bir soru olsun

You have three functions, which are all asynchronous:

- loadReport(id) which fetches the definition of a report

- runReport(report) which runs the report and returns a path to a PDF output file

- sendReport(filePath) which mails the file to subscribers and returns true if succeeded

Write code that executes a report using these three functions and shows alert if everything went well. Each of these functions can throw an exception. How would you handle it?

Şöyle yaparız

try {
  const report = await loadReport(id)
  const outputPath = await runReport(report)
  const completed = await sendReport(outputPath)
  alert(completed ? 'Done!' : 'Bad monkey!')
} catch (error) {
  alert(error.message)
}

Örnek
Şöyle yaparız. Her bir saniye de bir dizideki bir sayıyı döner. Çıktı olarak 5,4,3,2,1 alırız.

const delay = ms => new Promise(res => setTimeout(res, ms));
async function x() {
  const array = [1, 2, 3, 4, 5, 6, 7, 8].slice(0, 5);
  for (const item of array.reverse()) {
    console.log(item);
    await delay(1000);
  }
}

x()

Örnek
Elimizde şöyle bir kod olsun.

const getUserByImportMail = async (mail) => {
  const mailResult = ...
  ...
  return mailResult
}

Şöyle yaparız.

const isSenderValid = async mail => {
  const importMail = await getUserByImportMail({importMail: mail})
  ...
  // some checks
  return importMail
}

await yerine Promise.then kullanılabilir. Şöyle yaparız.

const isSenderValid = mail => {
  return getUserByImportMail({importMail: mail})
  .then(importMail => {
      ...
some checks
      return importMail
  });
}