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Promise

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Reference:developer.mozilla.org

Promise ​

Creating a function that returns a Promise:

js
function getUser() {
  return new Promise((resolve, reject) => {
    resolve({ id: 1 });
  });
}

Calling it and getting the result:

js
getUser().then((user) => {});

Wait all promises ​

First put all promises in an array:

ts
const promises: Promise<any>[] = [];
promises.push(fetch('example.com/1'));
promises.push(fetch('example.com/2'));
promises.push(fetch('example.com/3'));

Use this if the result of all promises are needed.

ts
Promise.allSettled(promises).then((results) => {
  results.forEach((result) => {
    if (result.status === 'fulfilled') {
      response = result.value;
    } else {
      error = result.reason;
    }
  });
});

Or this to stop as soon an any promise fails.

ts
Promise.all(promises).then((responses) => {
  // All promises resolved
}).catch((error) => {
  // First failed promise
});