JavaScript promises
JavaScript promises, async/await, and asynchronous flow
Learn JavaScript promises, async/await, asynchronous JavaScript, callbacks, promise chaining, error handling, Promise API methods, microtasks, generators, async iteration, the event loop, and Fetch API flow.
Promise and async/await lessons
Callbacks before promises
Start with callback-based asynchronous flow so promise syntax solves a concrete problem.
Outcome: Understand why deeply nested callback code becomes hard to compose and debug.
- JavaScript callbacks
- asynchronous JavaScript
- callback function
Promise basics
Learn promise states, fulfillment, rejection, executors, then handlers, and how promises represent future results.
Outcome: Model asynchronous work as a value that can settle later.
- JavaScript promises
- promise basics
- fulfilled rejected
Promise chaining
Pass values through then chains and compose asynchronous steps without deeply nested callbacks.
Outcome: Build sequential async logic that remains readable as it grows.
- promise chaining
- then chain
- asynchronous flow
Promise error handling
Handle rejected promises, propagation, recovery values, and catch placement deliberately.
Outcome: Design promise flows with clear success and failure paths.
- promise error handling
- catch promise
- rejected promise
Promise API
Use Promise.all, Promise.allSettled, Promise.race, Promise.any, and related helpers for combined async work.
Outcome: Choose the right Promise API method for parallel work, racing, and partial failures.
- Promise.all
- Promise.race
- Promise.allSettled
Microtasks
Understand how promise callbacks run in the microtask queue and how that affects execution order.
Outcome: Predict ordering between synchronous code, promises, timers, and rendering.
- microtasks
- microtask queue
- promise jobs
Async/await
Write promise-based code with async functions, await, try/catch, and sequential-looking control flow.
Outcome: Refactor promise chains into readable async functions without changing the underlying model.
- async await
- JavaScript async
- await promise
Generators
Learn paused function execution with generators and connect generator thinking to asynchronous iteration.
Outcome: Understand controllable iteration before studying async generators.
- JavaScript generators
- yield
- generator function
Async iterators and generators
Process asynchronous streams of values with async iteration and async generator syntax.
Outcome: Handle async data sources one value at a time with clear iteration flow.
- async iterators
- async generators
- for await
Event loop
Study tasks, microtasks, macrotasks, rendering, and the browser event loop behind asynchronous JavaScript.
Outcome: Explain why async callbacks run when they do and avoid ordering surprises.
- JavaScript event loop
- macrotasks
- microtasks
Fetch and promises
Use promise-based network requests, response parsing, aborting, progress, and HTTP error handling.
Outcome: Connect promise and async/await knowledge to real browser data loading.
- Fetch API
- JavaScript fetch
- async requests
Fetch API details
Go deeper into request and response objects, headers, methods, and browser fetch behavior.
Outcome: Build more deliberate client-side API calls after learning async control flow.
- Fetch API JavaScript
- Request Response
- HTTP fetch