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@andrew8088
Created February 15, 2024 14:56
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Managing Promise Concurrency in JavaScript
function mapPromises(args, callback, concurrency = 3) {
const { promise, resolve } = Promise.withResolvers();
const results = [];
let cursor = 0;
function next() {
if (cursor < args.length) {
const index = cursor++;
void callback(...args[index]).then(value => {
results[index] = { status: 'fulfilled', value };
}).catch(reason => {
results[index] = { status: 'rejecte', reason };
}).then(() => {
setImmediate(next);
});
} else if (args.length === results.length) {
resolve(results);
} else {
// no args remaining, but pending promises - just wait
}
}
while (concurrency--) {
next();
}
return promise;
}
@lnfel
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lnfel commented Feb 15, 2024

promise withResolvers FTW!

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