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Async/Await Summary

async/await is a modern way to work with asynchronous code in JavaScript. It helps you write code that looks synchronous but handles promises behind the scenes.

Example

async function myFunction() {
  const data = await axios.get('https://somerandomapi.com/somerandomdata');
  return data;
}

const result = await myFunction();

What Is a Promise?

A Promise is a built-in JavaScript object that represents the eventual result of an asynchronous operation.

Key Points:

  • A promise can be in one of three states:
    • Pending – the operation is still happening
    • Fulfilled – the operation completed successfully
    • Rejected – the operation failed
  • Promises are used to handle asynchronous operations, like fetching data from an API.

What Is an API?

An API (Application Programming Interface) lets you talk to another program or service to get or send data.

  • Always check the API documentation to know what URL to use and what data it returns.
  • Use try...catch to handle errors like broken connections or bad responses.

HTTP Status Codes

1xx – Informational

  • 100 Continue – The server has received the request headers. Keep going!

2xx – Success

  • 200 OK – Everything worked!
  • 201 Created – A new resource was successfully created (e.g., after a POST).
  • 204 No Content – The request was successful but there's no content to return.

3xx – Redirection

  • 301 Moved Permanently – The resource has been moved to a new URL.
  • 302 Found – Temporarily redirected.
  • 304 Not Modified – Use cached version; the resource hasn't changed.

4xx – Client Errors

  • 400 Bad Request – Something is wrong with your request.
  • 401 Unauthorized – You need to log in or provide an API key.
  • 403 Forbidden – You're not allowed to access this.
  • 404 Not Found – The resource doesn't exist.
  • 429 Too Many Requests – You're being rate-limited (slow down!).

5xx – Server Errors

  • 500 Internal Server Error – The server messed up.
  • 502 Bad Gateway – Server got an invalid response from another server.
  • 503 Service Unavailable – The server is down or busy.
  • 504 Gateway Timeout – The server took too long to respond.