Introduction to Promises

Promises are a fundamental concept in JavaScript that allows you to handle asynchronous operations in a more elegant and efficient way. In this article, we will explore the basics of promises, how they work, and provide examples of their usage.

A Promise is a JavaScript object that represents the eventual completion (success) or failure of an asynchronous operation — and lets you handle the result later.
It’s like a placeholder for a value that is not yet available but will be resolved in the future.

Example:-

let promise = new Promise(function(resolve, reject) {
  // async task...
  if (success) {
    resolve(result); //  task finished successfully
  } else {
    reject(error);   //  task failed
  }
});

States of a Promise

Consuming a Promise

ou are waiting for the result of an asynchronous operation and handling what happens next — whether it succeeds or fails.

promise
  .then(function(result) {
    // handles success
  })
  .catch(function(error) {
    // handles failure
  });

Example: Creating and Using a Promise

function orderPizza() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      const available = true;

      if (available) {
        resolve("Pizza is ready!");
      } else {
        reject("Pizza shop is closed.");
      }
    }, 2000);
  });
}

// Consume the promise
orderPizza()
  .then((message) => {
    console.log("Success:", message);
  })
  .catch((error) => {
    console.log("Error:", error);
  });

Why use Promise