Let's Learn Generators in JavaScript 🚀

Hey, JavaScript enthusiasts! 👋 Are you ready to supercharge your coding skills? Today, we’re diving into Generators — a special kind of function in JavaScript. Don’t worry, it’s not rocket science 🚀 (but it’s close)! Let’s cut the jargon and get straight to the action.

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What Are Generators? 🤔

In simple terms, Generators are functions that can pause and resume their execution. Unlike regular functions that run from start to finish, generators give you more control.

How? By using the magic of the function* syntax and the yield keyword. Let’s see them in action!

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Writing Your First Generator Function 🛠️

function* myFirstGenerator() {
  yield "Hello 🌟";
  yield "Generators are awesome!";
  yield "Goodbye 👋";
}

// Let's use it!
const gen = myFirstGenerator();

console.log(gen.next()); // { value: 'Hello 🌟', done: false }
console.log(gen.next()); // { value: 'Generators are awesome!', done: false }
console.log(gen.next()); // { value: 'Goodbye 👋', done: false }
console.log(gen.next()); // { value: undefined, done: true }

What’s Happening Here?

1. The yield keyword acts as a pause point in your function.
2. Each call to gen.next() moves the function to the next yield.
3. When there are no more yield statements, the generator returns { done: true }.

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Practical Use Cases 🎯

1. Infinite Series Generators ♾️

Ever wanted to generate infinite numbers without blowing up your memory? Generators to the rescue!

function* infiniteNumbers() {
  let num = 1;
  while (true) {
    yield num++;
  }
}

const numbers = infiniteNumbers();

console.log(numbers.next().value); // 1
console.log(numbers.next().value); // 2
console.log(numbers.next().value); // 3
// ... and so on

2. Controlled Iteration for Data Fetching 📡

Need to fetch data in chunks or lazy load something? Generators can help:

function* fetchInChunks(data) {
  for (let i = 0; i < data.length; i += 2) {
    yield data.slice(i, i + 2);
  }
}

const chunks = fetchInChunks([1, 2, 3, 4, 5, 6, 7, 8]);

console.log(chunks.next().value); // [1, 2]
console.log(chunks.next().value); // [3, 4]
console.log(chunks.next().value); // [5, 6]

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Fun with Delegating Generators 🤹‍♀️

Generators can call other generators using yield*. Let’s make them work together:

function* innerGenerator() {
  yield "I’m the inner generator 🎯";
}

function* outerGenerator() {
  yield "I’m the outer generator 🌟";
  yield* innerGenerator();
  yield "Back to the outer generator 👋";
}

const gen = outerGenerator();

for (const value of gen) {
  console.log(value);
}

Output:

I’m the outer generator 🌟  
I’m the inner generator 🎯  
Back to the outer generator 👋  

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Why Use Generators? 🤷‍♂️

1. Lazy Evaluation: Generate values only when needed.
2. Better Performance: No need to calculate all results upfront.
3. Asynchronous Flow: Combine with async/await for cleaner async code.

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Trick Question for You! 🤔💡

Can a generator function be asynchronous? If yes, how would you use it?

Drop your answers in the comments or try it out in your code! 🧑‍💻

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Wrap-Up 🎉

Generators might seem a bit tricky at first, but with some practice, they can become a powerful tool in your JavaScript arsenal. Start small, explore their possibilities, and soon you'll be wielding them like a pro! 💪

Do you have a cool use case for generators? Share it with us in the comments below! Let’s learn together. 🙌

Happy coding! 💻✨

Comments

[Sohail SJ | chakraframer.com]

Damn, these are so powerful, I can think of n number of ways to use this like a progress bar and infinite scroll block with dynamic data fetching. thanks @jagroop2001

[Jagroop Singh]

You're welcome! @thesohailjafri

[Sohail SJ | chakraframer.com]

learning new things every day from you, keep it up bro <3

[JosefJarman]

Here’s a comment for "Let's Learn Generators in JavaScript":

// This tutorial introduces JavaScript generators, a powerful feature for handling asynchronous operations and managing state. 
// Generators allow you to pause and resume functions at any point, making them [ideal](https://kukasoittii.fi/) for tasks like lazy evaluation and complex iteration. 
// The 'function*' syntax and the 'yield' keyword are key to creating generator functions. 
// Understanding generators helps improve code efficiency and readability when working with asynchronous programming.

[Philip]

This is an excellent and engaging introduction to JavaScript Generators! 🚀 Generators are powerful for tasks like lazy evaluation and asynchronous flow, and with EchoAPI, you can efficiently test and mock APIs that use generator functions, simplifying your development and debugging process.

[Itamar Tati]

What's a real world use case for Generators

[Peter Vivo]

redux-saga is great generator based library extending by redux with async state handling for complex busines logic.

I write a POC program - long time ago, when generator released in JS :
poker game poc, with generators and regexp
The main game loop was solved with generator.

[Dan Maroff]

Fantastic! Didn’t know this functionality existed in JavaScript 😀

[Slobi]

Level up content!