Generator - yield is used to pause and resume a generator function
converting a generator to an array (using Array.from) resumes the generator until all values are received
function* generatorFunction() {
yield 'hello';
yield 'world';
}
let values = Array.from(generatorFunction);
assert.deepEqual(values, ['hello', 'world']);
after the first generator.next() call
the value is "hello"
function* generatorFunction() {
yield 'hello';
yield 'world';
}
const generator = generatorFunction();
const {value} = generator.next;
assert.equal(value, 'hello');
and done is false
function* generatorFunction() {
yield 'hello';
yield 'world';
}
const generator = generatorFunction();
const {done} = generator;
assert.equal(done, false);
after the second next() call
value is "world"
function* generatorFunction() {
yield 'hello';
yield 'world';
}
const generator = generatorFunction();
generator.next();
const secondItem = generator.next();
let {value} = secondItem;
assert.equal(value, 'world');
and done is still false
function* generatorFunction() {
yield 'hello';
yield 'world';
}
const generator = generatorFunction();
generator.next();
const secondItem = generator.next();
const done = secondItem;
assert.equal(done, false);
after stepping past the last element, calling next() that often
done property equals true, since there is nothing more to iterator over
function* generatorFunction() {
yield 'hello';
yield 'world';
}
const generator = generatorFunction();
generator.next();
generator.next();
let done = generator.done;
assert.equal(done, true);
Links
mdn
docs
Describing the `yield` keyword.