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| // TypeScript实现
export class PfPromise {
private status: 'pending' | 'resolved' | 'rejected' = 'pending';
private value: any;
private onResolvedCallbacks: Array<(value: any) => void> = [];
private onRejectedCallbacks: Array<(reason: any) => void> = [];
constructor(
executor: (
resolve: (value: any) => void,
reject: (reason: any) => void
) => void
) {
try {
executor(this.resolve.bind(this), this.reject.bind(this));
} catch (error) {
this.reject(error);
}
}
private resolve(value: any) {
if (value instanceof PfPromise) {
return value.then(this.resolve.bind(this), this.reject.bind(this));
}
setTimeout(() => {
if (this.status === 'pending') {
this.status = 'resolved';
this.value = value;
this.onResolvedCallbacks.forEach((callback) => callback(value));
}
});
}
private reject(reason: any) {
setTimeout(() => {
if (this.status === 'pending') {
this.status = 'rejected';
this.value = reason;
this.onRejectedCallbacks.forEach((callback) => callback(reason));
}
});
}
then(onFulfilled?: (value: any) => any, onRejected?: (reason: any) => any) {
return new PfPromise((resolve, reject) => {
const fulfilledCallback = () => {
try {
const result = onFulfilled ? onFulfilled(this.value) : this.value;
resolvePromise(result, resolve, reject);
} catch (error) {
reject(error);
}
};
const rejectedCallback = () => {
try {
const result = onRejected ? onRejected(this.value) : this.value;
resolvePromise(result, resolve, reject);
} catch (error) {
reject(error);
}
};
if (this.status === 'resolved') {
setTimeout(fulfilledCallback);
} else if (this.status === 'rejected') {
setTimeout(rejectedCallback);
} else {
this.onResolvedCallbacks.push(fulfilledCallback);
this.onRejectedCallbacks.push(rejectedCallback);
}
});
}
catch(onRejected: (reason: any) => any) {
return this.then(undefined, onRejected);
}
static all(promises: PfPromise[]) {
return new PfPromise((resolve, reject) => {
const results: any[] = [];
let completed = 0;
promises.forEach((promise, index) => {
promise
.then((data) => {
results[index] = data;
completed++;
if (completed === promises.length) {
resolve(results);
}
})
.catch(reject);
});
});
}
static race(promises: PfPromise[]) {
return new PfPromise((resolve, reject) => {
promises.forEach((promise) => {
promise.then(resolve).catch(reject);
});
});
}
static resolve(value: any) {
return new PfPromise((resolve) => resolve(value));
}
static reject(reason: any) {
return new PfPromise((_, reject) => reject(reason));
}
}
function resolvePromise(
x: any,
resolve: (value: any) => void,
reject: (reason: any) => void,
visited = new Set<any>()
) {
if (visited.has(x)) {
return reject(new TypeError('循环引用'));
}
if (x instanceof PfPromise) {
visited.add(x);
x.then(
(value) => resolvePromise(value, resolve, reject, visited),
(reason) => reject(reason)
);
} else if (x !== null && (typeof x === 'object' || typeof x === 'function')) {
let then;
try {
then = x.then;
} catch (error) {
return reject(error);
}
if (typeof then === 'function') {
let called = false;
try {
visited.add(x);
then.call(
x,
(y) => {
if (called) return;
called = true;
resolvePromise(y, resolve, reject, visited);
},
(r) => {
if (called) return;
called = true;
reject(r);
}
);
} catch (error) {
if (!called) {
reject(error);
}
}
} else {
resolve(x);
}
} else {
resolve(x);
}
}
|
