Understanding JavaScript Promises (With a Desi Twist 🌟)

Inder Rajoriya — Wed, 08 Jan 2025 18:07:06 +0000

Radhe Radhe Guy's

JavaScript Promises can sometimes feel like that one friend who says, "Bhai, kaam ho jayega!" but leaves you waiting forever. This post will break down promises in a fun and easy way with relatable Indian examples.

1. `What is a Promise in JavaScript?`

A Promise in JavaScript is like ordering biryani online. It will either:

Resolve – Biryani arrives and you're happy 😋.

Reject – Delivery guy cancels, and you're left starving 😭.

Example:

const biryaniOrder = new Promise((resolve, reject) => {
  let biryaniReady = true;

  if (biryaniReady) {
    resolve('Biryani is here!');
  } else {
    reject('No biryani for you today.');
  }
});

2. `Consuming a Promise (Then and Catch)`

To handle a Promise, we use .then() and .catch().

Example:

biryaniOrder
  .then((message) => {
    console.log(message); // Biryani is here!
  })
  .catch((error) => {
    console.log(error); // No biryani for you today.
  });

Relatable? Imagine this:

"When Zomato says 'Arriving in 10 mins' but it's been 30 mins..."

3. `Promise Chaining (One Thing After Another)`

Promise chaining allows sequential execution. Like ordering dessert after biryani.

Example:

biryaniOrder
  .then((message) => {
    console.log(message);
    return 'Let’s order gulab jamun!';
  })
  .then((dessert) => {
    console.log(dessert); // Let's order gulab jamun!
  })
  .catch((error) => {
    console.log(error);
  });

when the Gulab jamun is coming😋

4. `Async/Await (The VIP Treatment)`

Async/await simplifies working with promises, like being a VVIP at a wedding.

Example:

async function enjoyMeal() {
  try {
    let food = await biryaniOrder;
    console.log(food);
    console.log('Gulab jamun coming next...');
  } catch (error) {
    console.log(error);
  }
}

enjoyMeal();

5. `Why Use Promises?`

Better readability (No callback hell 😈)
Easier error handling
Clean asynchronous operations

When your relatives promise shaadi ki laddoo but ghost you later.

Thanks for reading! 🤍✌️

Understanding req.params, req.query, and req.body in Express

Inder Rajoriya — Tue, 24 Sep 2024 11:08:30 +0000

Radhe Radhe Guy's

These three, req.body, req.query and req.params are part of Express request object.
They are used by the client to send data to the server.
This post outlines their differences and gives examples on how to use them.

1. `req.body`

Generally used in POST/PUT requests.
Use it when you want to send sensitive data(eg. form data) or super long JSON data to the server.

How to send data in the request body:

Using curl:

  curl -d '{"key1":"value1", "key2":"value2"}' -H "Content-Type: application/json" -X POST http://localhost:3000/inder

Using axios:

  axios.post('/inder', {
    key1: 'value1',
    key2: 'value2'
  })
  .then(response => {
    // handle response
  })
  .catch(error => {
    // handle error
  });

How to access data from req.body:

app.post('/inder', (req, res) => {
  console.log(req.body.key1); // Output: value1
  console.log(req.body.key2); // Output: value2
});

Remember: You need to use the express.json() middleware to parse JSON bodies.

app.use(express.json());

2. `req.params`

This is used for named route parameters, which are part of the URL path.
Route parameters are great for passing data in dynamic routes, such as IDs or resource names.

Example:

app.get('/inder/:number', (req, res) => {
  console.log(req.params.number); // Outputs the value of `number` from the URL
});

Client request:

GET http://localhost:3000/inder/1

3. `req.query`

req.query is commonly used for querying/filtering data, like pagination, sorting, or filtering API responses. It's passed as key-value pairs in the URL.

Example:

app.get('/animals', (req, res) => {
  console.log(req.query.page); // Output: 10
});

Client request:

GET http://localhost:3000/animals?page=10

Each of these properties has a specific use case and is essential for managing different types of client-server communication in Express.

Thanks for reading! 🤍🤞🏻

DEV Community: Inder Rajoriya

Understanding JavaScript Promises (With a Desi Twist 🌟)

1. What is a Promise in JavaScript?

2. Consuming a Promise (Then and Catch)

3. Promise Chaining (One Thing After Another)

4. Async/Await (The VIP Treatment)

5. Why Use Promises?

Understanding req.params, req.query, and req.body in Express

1. req.body

2. req.params

3. req.query

1. `What is a Promise in JavaScript?`

2. `Consuming a Promise (Then and Catch)`

3. `Promise Chaining (One Thing After Another)`

4. `Async/Await (The VIP Treatment)`

5. `Why Use Promises?`

1. `req.body`

2. `req.params`

3. `req.query`