JavaScript Generators

JavaScript Generators are a powerful new feature of the JavaScript language. They allow you to write code that can pause and resume, making it easier to write asynchronous code. Generators are a great way to simplify complex asynchronous tasks and make your code more readable.

Why should you use it?

Generators make asynchronous code easier to read and write.
Generators make it easier to handle errors in asynchronous code.
Generators can be used to create custom iterators.

Generators

Generators are functions that can be paused and resumed. They are a special type of function that can be used to create iterators. Generators are a great way to create iterators that can be controlled and provide a more efficient way of creating and managing iterators.

Generators are declared using the function* keyword. This is followed by the generator's name and a set of parentheses. Generators can also take arguments, just like a normal function.

script.js

function* generator() {
  console.log('Generator started');
  yield;
  console.log('Generator resumed');
}

Generators are different from normal functions in that they can be paused and resumed. This is done using the yield keyword. The yield keyword pauses the generator and returns a value. The generator can then be resumed by calling the next() method on the generator.

script.js

function* generator() {
  console.log('Generator started');
  const value = yield 'Hello World';
  console.log('Generator resumed');
  console.log(value);
}

Generators can also take arguments. This is done by passing the arguments to the next() method. The arguments are then available to the generator as the value property of the object returned by the next() method.

script.js

function* generator() {
  console.log('Generator started');
  const value = yield;
  console.log('Generator resumed');
  console.log(value);
}

const gen = generator();
gen.next();
gen.next('Hello World');

Generators can also be used to create iterators. This is done by using the for..of loop. The for..of loop will loop over the values returned by the generator until the generator is exhausted.

script.js

function* generator() {
  yield 1;
  yield 2;
  yield 3;
}

const gen = generator();

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

Generators can also be used with the Promise API. This is done by using the Promise.coroutine() method. The Promise.coroutine() method takes a generator and returns a Promise that will be resolved when the generator is exhausted.

script.js

function* generator() {
  const value = yield Promise.resolve('Hello World');
  console.log(value);
}

const gen = generator();

Promise.coroutine(gen)();

Generators are a great way to create and manage iterators. They provide a more efficient way of creating and managing iterators and can be used with the Promise API.