finally

When the promise is settled, i.e either fulfilled or rejected, the specified callback function is executed. This provides a way for code to be run whether the promise was fulfilled successfully or rejected once the Promise has been dealt with.3

function findDataById(id) {
  return new Promise(function (resolve, reject) {
    let sampleData = [1, 2, 3, 4, 5];
    if (sampleData[id]) {
      resolve(sampleData[id]);
    } else {
      reject(new Error('Invalid id'));
    }
  });
}

findDataById(4)
  .then(function (response) {
    console.log(response);
  })
  .catch(function (err) {
    console.error(err);
  })
  .finally(function () {
    console.log('Promise completed');
  });

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References

• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/finally