Created
January 26, 2023 01:03
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Implementation of Promise static methods
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| function promisesAll(promisesCollection) { | |
| return new Promise((resolve, reject) => { | |
| const resolved = []; | |
| promisesCollection.forEach((promise, index) => { | |
| promise | |
| .then((value) => { | |
| resolved.push({ index, value }); | |
| if (resolved.length === promisesCollection.length) { | |
| resolve(restoreArray(resolved)); | |
| } | |
| }) | |
| .catch((err) => { | |
| reject(err); | |
| }); | |
| }); | |
| }); | |
| } | |
| function promisesAny(promisesCollection) { | |
| return new Promise((resolve, reject) => { | |
| const rejected = []; | |
| promisesCollection.forEach((promise, index) => { | |
| promise | |
| .then((value) => { | |
| resolve(value); | |
| }) | |
| .catch((err) => { | |
| rejected.push({ index, value: err }); | |
| if (rejected.length === promisesCollection.length) { | |
| reject(new AggregateError(restoreArray(rejected))); | |
| } | |
| }); | |
| }); | |
| }); | |
| } | |
| function promisesAllSettled(promisesCollection) { | |
| return new Promise((resolve) => { | |
| const state = []; | |
| promisesCollection.forEach((promise, index) => { | |
| promise | |
| .then((value) => { | |
| state.push({ | |
| index, | |
| value: { | |
| status: 'fulfilled', | |
| value, | |
| }, | |
| }); | |
| }) | |
| .catch((reason) => { | |
| state.push({ | |
| index, | |
| value: { | |
| status: 'rejected', | |
| reason, | |
| }, | |
| }); | |
| }) | |
| .then(() => { | |
| if (state.length === promisesCollection.length) { | |
| resolve(restoreArray(state)); | |
| } | |
| }); | |
| }); | |
| }); | |
| } | |
| function promisesRace(promisesCollection) { | |
| return new Promise((resolve, reject) => { | |
| let isSettled = false; | |
| promisesCollection.forEach((promise) => { | |
| promise | |
| .then((value) => { | |
| if (isSettled) return; | |
| isSettled = true; | |
| resolve(value); | |
| }) | |
| .catch((err) => { | |
| if (isSettled) return; | |
| isSettled = true; | |
| reject(err); | |
| }); | |
| }); | |
| }); | |
| } | |
| function promisesSomeCount(promisesCollection, count) { | |
| return new Promise((resolve, reject) => { | |
| const resolved = []; | |
| const rejected = []; | |
| promisesCollection.forEach((promise) => { | |
| promise | |
| .then((value) => { | |
| resolved.push(value); | |
| if (resolved.length === count) { | |
| resolve(resolved); | |
| } | |
| }) | |
| .catch((err) => { | |
| rejected.push(err); | |
| if (rejected.length > promisesCollection.length - count) { | |
| reject(new AggregateError(rejected)) | |
| } | |
| }); | |
| }); | |
| }); | |
| } | |
| function restoreArray(collection) { | |
| return collection.reduce((acc, { index, value }) => { | |
| acc[index] = value; | |
| return acc; | |
| }, []); | |
| } | |
| class MyOwnPromise { | |
| static all(promises) { return promisesAll(promises); } | |
| static any(promises) { return promisesAny(promises); } | |
| static allSettled(promises) { return promisesAllSettled(promises); } | |
| static race(promises) { return promisesRace(promises); } | |
| static someCount(promises, count) { return promisesSomeCount(promises, count); } | |
| } |
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