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61 lines
1.3 KiB
61 lines
1.3 KiB
/** |
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* Given an AsyncIterable and a callback function, return an AsyncIterator |
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* which produces values mapped via calling the callback function. |
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*/ |
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export function mapAsyncIterator(iterable, callback) { |
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const iterator = iterable[Symbol.asyncIterator](); |
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async function mapResult(result) { |
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if (result.done) { |
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return result; |
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} |
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try { |
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return { |
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value: await callback(result.value), |
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done: false, |
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}; |
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} catch (error) { |
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/* c8 ignore start */ |
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// FIXME: add test case |
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if (typeof iterator.return === 'function') { |
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try { |
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await iterator.return(); |
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} catch (_e) { |
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/* ignore error */ |
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} |
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} |
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throw error; |
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/* c8 ignore stop */ |
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} |
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} |
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return { |
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async next() { |
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return mapResult(await iterator.next()); |
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}, |
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async return() { |
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// If iterator.return() does not exist, then type R must be undefined. |
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return typeof iterator.return === 'function' |
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? mapResult(await iterator.return()) |
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: { |
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value: undefined, |
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done: true, |
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}; |
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}, |
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async throw(error) { |
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if (typeof iterator.throw === 'function') { |
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return mapResult(await iterator.throw(error)); |
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} |
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throw error; |
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}, |
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[Symbol.asyncIterator]() { |
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return this; |
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}, |
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}; |
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}
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