JAVASCRIPT

Generator function

function* indexGenerator(){
  var index = 0;
  while(true) {
    yield index++;
  }
}
const g = indexGenerator();
console.log(g.next().value); // => 0
console.log(g.next().value); // => 1

What is a generator function?

function xrange($min, $max) {
    for ($i = $min; $i <= $max; $i++) {
        yield $i;
    }
}

//[…]

foreach (xrange(1, 10) as $key => $value) {
    echo "$key => $value" . PHP_EOL;
}

generator function

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

const gen = generator(); // "Generator { }"

console.log(gen.next().value); // 1
console.log(gen.next().value); // 2
console.log(gen.next().value); // 3