I have an async generator function defined, and want to create a second async generator function that is a partial application of the first function. For example, this works:
async function* fn1(a, b) {/* do something */}
async function* fn2() {
const a1 = fn1(0, 0);
for await (const value of a1) {
yield value;
}
}
My question is: is there a more concise way to define fn2
?
fn1
returns the async iterable that fn2
is iterating over, so rather than iterating manually in fn2
, you can just yield the iterable created from fn1
and let fn2
's consumer handle it:
async function* fn2() {
yield* fn1(0, 0);
}
const delay = ms => new Promise(res => setTimeout(res, ms));
async function* fn1(a, b) {
for (let i = 0; i < 3; i++) {
await delay(1000);
yield i;
}
}
async function* fn2() {
yield* fn1(0, 0);
}
(async () => {
for await (const val of fn2()) {
console.log('Consumer got', val);
}
console.log('Done');
})();
// Original version, without yield* (just to illustrate equivalence):
const delay = ms => new Promise(res => setTimeout(res, ms));
async function* fn1(a, b) {
for (let i = 0; i < 3; i++) {
await delay(1000);
yield i;
}
}
async function* fn2() {
const a1 = fn1(0, 0);
for await (const value of a1) {
yield value;
}
}
(async () => {
for await (const val of fn2()) {
console.log('Consumer got', val);
}
console.log('Done');
})();