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| const PENDING = "pending"; const FULFILLED = "fulfilled"; const REJECTED = "rejected";
export default class MyPromise { constructor(executor) { try { executor(this.resolve, this.reject); } catch (e) { this.reject(e); } }
status = PENDING; value = undefined; reason = undefined; successCallback = []; failCallback = [];
resolve = (value) => { if (this.status !== PENDING) return; this.status = FULFILLED; this.value = value; while (this.successCallback.length) this.successCallback.shift()(); }; reject = (reason) => { if (this.status !== PENDING) return; this.status = REJECTED; this.reason = reason; while (this.failCallback.length) this.failCallback.shift()(); };
then(successCallback, failCallback) { successCallback = successCallback ? successCallback : (value) => value; failCallback = failCallback ? failCallback : (reason) => { throw reason; }; let promsie2 = new MyPromise((resolve, reject) => { if (this.status === FULFILLED) { setTimeout(() => { try { let x = successCallback(this.value); resolvePromise(promsie2, x, resolve, reject); } catch (e) { reject(e); } }, 0); } else if (this.status === REJECTED) { setTimeout(() => { try { let x = failCallback(this.reason); resolvePromise(promsie2, x, resolve, reject); } catch (e) { reject(e); } }, 0); } else { this.successCallback.push(() => { setTimeout(() => { try { let x = successCallback(this.value); resolvePromise(promsie2, x, resolve, reject); } catch (e) { reject(e); } }, 0); }); this.failCallback.push(() => { setTimeout(() => { try { let x = failCallback(this.reason); resolvePromise(promsie2, x, resolve, reject); } catch (e) { reject(e); } }, 0); }); } }); return promsie2; }
finally(callback) { return this.then( (value) => { return MyPromise.resolve(callback()).then(() => value); }, (reason) => { return MyPromise.resolve(callback()).then(() => { throw reason; }); } ); }
catch(failCallback) { return this.then(undefined, failCallback); }
static all(array) { let result = []; let index = 0; return new MyPromise((resolve, reject) => { function addData(key, value) { result[key] = value; index++; if (index === array.length) { resolve(result); } }
for (let i = 0; i < array.length; i++) { let current = array[i]; if (current instanceof MyPromise) { current.then( (value) => addData(i, value), (reason) => reject(reason) ); } else { addData(i, array[i]); } } }); }
static resolve(value) { if (value instanceof MyPromise) return value; return new MyPromise((resolve) => resolve(value)); } }
function resolvePromise(promsie2, x, resolve, reject) { if (promsie2 === x) { return reject( new TypeError("Chaining cycle detected for promise #<Promise>") ); } if (x instanceof MyPromise) { x.then(resolve, reject); } else { resolve(x); } }
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