Best of Modern JavaScript — Generators as Producers

Generators are useful for producing data.

Since 2015, JavaScript has improved immensely.

It’s much more pleasant to use it now than ever.

In this article, we’ll look at JavaScript generators.

Generators as Iterators

We can use generator functions as iterators.

For instance, we can write:

function* genFn() {
  yield 'foo';
  yield 'bar';
  yield 'baz';
}
const gen = genFn();
console.log(gen.next());
console.log(gen.next());

to create a generator function and a generator.

genFn is the generator function as indicated with the function* keyword.

The function returns a generator with the genFn call.

Then we call next to get the next item on the list.

The yield keyword lets us return the value with the next method call.

Therefore, we get:

{value: "foo", done: false}
{value: "bar", done: false}

to get the yielded items via the value property.

We can also access the yielded values with the for-of loop.

For example, we can write:

function* genFn() {
  yield 'foo';
  yield 'bar';
  yield 'baz';
}
const gen = genFn();
for (const x of gen) {
  console.log(x);
}

Then we get:

foo
bar
baz

logged.

programming technology javascript

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