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yield

Baseline

20169

yield

function* foo(index) {
  while (index < 2) {
    yield index;
    index++;
  }
}

const iterator = foo(0);

console.log(iterator.next().value);
// : 0

console.log(iterator.next().value);
// : 1

yield
yield expression

expression: undefined

next()

: next() yield yield next() yield

yield yield return

yield

Generator next()

yield next() value done 2 value yield done false
next() value undefined done true
return next() value done true
throw next()

yield next() next() yield next() yield next()

return() throw() return throw yield try...catch...finally return() throw() yield next()

yield

function* countAppleSales() {
  const saleList = [3, 7, 5];
  for (const sale of saleList) {
    yield sale;
  }
}

const appleStore = countAppleSales(); // Generator { }
console.log(appleStore.next()); // { value: 3, done: false }
console.log(appleStore.next()); // { value: 7, done: false }
console.log(appleStore.next()); // { value: 5, done: false }
console.log(appleStore.next()); // { value: undefined, done: true }

next(value) step yield next() next()

function* counter(value) {
  while (true) {
    const step = yield value++;

    if (step) {
      value += step;
    }
  }
}

const generatorFunc = counter(0);
console.log(generatorFunc.next().value); // 0
console.log(generatorFunc.next().value); // 1
console.log(generatorFunc.next().value); // 2
console.log(generatorFunc.next().value); // 3
console.log(generatorFunc.next(10).value); // 14
console.log(generatorFunc.next().value); // 15
console.log(generatorFunc.next(10).value); // 26


ECMAScript 2027 LanguageSpecification # prod-YieldExpression

MDN

MDN 2025916

GitHub