@types/q

Creating Promises

This feature allows you to create a new promise using Q.defer(). The deferred object has a promise property that can be used to attach handlers for the resolved and rejected states.

const Q = require('q');
const deferred = Q.defer();
deferred.promise.then((value) => {
  console.log('Resolved with:', value);
}).catch((error) => {
  console.error('Rejected with:', error);
});
deferred.resolve('Success');

Chaining Promises

This feature demonstrates how to chain multiple promises together using Q.fcall() and .then(). Each step in the chain can return a value or a new promise, allowing for sequential asynchronous operations.

const Q = require('q');
Q.fcall(() => {
  return 'First step';
}).then((result) => {
  console.log(result);
  return 'Second step';
}).then((result) => {
  console.log(result);
  return 'Third step';
}).then((result) => {
  console.log(result);
}).catch((error) => {
  console.error('Error:', error);
});

Handling Multiple Promises

This feature shows how to handle multiple promises concurrently using Q.all(). It waits for all promises in the array to resolve and then returns an array of results. If any promise is rejected, it will catch the error.

const Q = require('q');
const promise1 = Q.delay(1000).then(() => 'First');
const promise2 = Q.delay(2000).then(() => 'Second');
Q.all([promise1, promise2]).then((results) => {
  console.log('All promises resolved:', results);
}).catch((error) => {
  console.error('One or more promises rejected:', error);
});