How Can I Wait for Multiple JavaScript Promises to Finish Before Continuing?-JS Tutorial-php.cn

How Can I Wait for Multiple JavaScript Promises to Finish Before Continuing?

Barbara Streisand

Release： 2024-12-19 00:16:09

Original

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How Can I Wait for Multiple JavaScript Promises to Finish Before Continuing?

Waiting for Multiple Asynchronous Tasks to Complete in JavaScript

Problem:

You have a series of asynchronous tasks (promises) and need to execute a block of code only when all of them have been completed.

Solution:

Use Promise.all to collect all promises into a single array and wait for its resolution or rejection.

Implementation:

const promises = [];

for (let i = 0; i < 5; i++) {
  promises.push(doSomeAsyncStuff());
}

Promise.all(promises)
  .then(() => {
    for (let i = 0; i < 5; i++) {
      doSomeStuffOnlyWhenTheAsyncStuffIsFinish();
    }
  })
  .catch((e) => {
    // Handle errors here
  });

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Revised doSomeAsyncStuff function:

function doSomeAsyncStuff() {
  return new Promise((resolve, reject) => {
    const editor = generateCKEditor();
    editor.on('instanceReady', (evt) => {
      doSomeStuff();
      resolve(true);
    })
  });
}

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Example:

function doSomethingAsync(value) {
  return new Promise((resolve) => {
    setTimeout(() => {
      console.log("Resolving " + value);
      resolve(value);
    }, Math.floor(Math.random() * 1000));
  });
}

function test() {
  const promises = [];

  for (let i = 0; i < 5; i++) {
    promises.push(doSomethingAsync(i));
  }

  Promise.all(promises)
    .then((results) => {
      console.log("All done", results);
    })
    .catch((e) => {
      // Handle errors here
    });
}

test();

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