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The Complete Guide to Modern JavaScript

Generators

In this lesson you’ll learn all about generators and what to do with them.

We'll cover the following...

What is a generator? #

A generator function is a function that we can start and stop, for an indefinite amount of time. And also restart with the possibility of passing additional data at a later point in time.

To create a generator function we write like this:

Javascript (babel-node)
function* fruitList(){
  yield 'Banana';
  yield 'Apple';
  yield 'Orange';
}
const fruits = fruitList();
fruits;
// Generator
console.log(fruits.next());
// Object { value: "Banana", done: false }
console.log(fruits.next());
// Object { value: "Apple", done: false }
console.log(fruits.next());
// Object { value: "Orange", done: false }
console.log(fruits.next());
// Object { value: undefined, done: true }

Let’s have a look at the code piece by piece:

  • we declared the function using function*
  • we used the keyword yield before our content
  • we start our function using .next()
  • the last time we call .next() we receive and empty object and we get
...