Discover Promises in Bnlang

A Promise in Bnlang represents a value that may be available now, later, or never.
It is a structured way to handle asynchronous operations without falling into callback nesting.
A promise has three states: pending, fulfilled, and rejected.

Creating a Promise

const myPromise = new Promise((resolve, reject) => {
  const success = true;
  if (success) {
    resolve("Operation successful!");
  } else {
    reject("Operation failed!");
  }
});

myPromise.then((msg) => console.log(msg))
         .catch((err) => console.error(err));

Chaining Promises

Promises can be chained using .then() to handle sequences of asynchronous tasks.

new Promise((resolve) => resolve(2))
  .then((n) => n * 2)
  .then((n) => n * 3)
  .then((result) => console.log(result)); // 12

Promise.all

Promise.all runs multiple promises in parallel and resolves when all are fulfilled.
If any fail, the whole promise rejects.

Promise.all([
  Promise.resolve(1),
  Promise.resolve(2),
  Promise.resolve(3),
]).then((values) => console.log(values)); // [1,2,3]

Best Practices

  • Always handle errors with .catch() to avoid unhandled rejections.
  • Use Promise.all or Promise.race for running tasks together.
  • Keep promises short and focused for readability.