Generators

⬅️ Execute Program Modern JavaScript

Generators

// The * in function* marks our function as a generator.
function* numbers() {
  // Each yield in the generator provides one value to the loop.
  yield 1;
  yield 2;
  yield 3;
}
 
// generators are iterable
const results = [];
for (const n of numbers()) {
  results.push(n);
}
results;
 
//Result:
[1, 2, 3]
 
// converted to an array
function* letters() {
  yield 'a';
  yield 'b';
}
Array.from(letters());
 
Result:
 
['a', 'b']
 
// another example
function* numbers() {
  let x = 1;
  yield x;
  x += 1;
  yield x;
}
Array.from(numbers());
 
// Result:
[1, 2]
 
// and another one
function* numbersBelow(maximum) {
  for (let i=0; i<maximum; i++) {
    yield i;
  }
}
Array.from(numbersBelow(3));
 
Result:
 
[0, 1, 2]
 

• yield is like return but we can do it multiple times