const PROMISE_STATUS_PENDING = 'pending';
const PROMISE_STATUS_FULFILLED = 'fulfilled';
const PROMISE_STATUS_REJECTED = 'rejected';
function execFunctionWithCatchError(execFun, value, resolve, reject) {
try {
const result = execFun(value);
resolve(result);
}
catch (error) {
reject(error);
}
}
class MyPromise {
constructor(executor) {
this.status = PROMISE_STATUS_PENDING;
this.value = undefined;
this.reason = undefined;
this.onFulfilledFns = [];
this.onRjectedFns = [];
const resolve = value => {
if (this.status === PROMISE_STATUS_PENDING) {
queueMicrotask(() => {
if (this.status !== PROMISE_STATUS_PENDING) {
return;
}
this.status = PROMISE_STATUS_FULFILLED;
this.value = value;
this.onFulfilledFns.forEach(fn => {
fn(this.value);
});
});
}
};
const reject = reason => {
if (this.status === PROMISE_STATUS_PENDING) {
queueMicrotask(() => {
if (this.status !== PROMISE_STATUS_PENDING) {
return;
}
this.status = PROMISE_STATUS_REJECTED;
this.reason = reason;
this.onRjectedFns.forEach(fn => {
fn(this.reason);
});
});
}
};
try {
executor(resolve, reject);
} catch (error) {
reject(error);
}
}
then(onFulfilled, onRjected) {
onFulfilled = onFulfilled || (value => {
return value;
});
onRjected = onRjected || (err => {
throw err;
});
return new MyPromise((resolve, reject) => {
if (this.status === PROMISE_STATUS_FULFILLED && onFulfilled) {
execFunctionWithCatchError(onFulfilled, this.value, resolve, reject);
}
if (this.status === PROMISE_STATUS_REJECTED && onRjected) {
execFunctionWithCatchError(onRjected, this.value, resolve, reject);
}
if (this.status === PROMISE_STATUS_PENDING) {
if (onFulfilled) {
this.onFulfilledFns.push(() => {
execFunctionWithCatchError(onFulfilled, this.value, resolve, reject);
});
}
if (onRjected) {
this.onRjectedFns.push(() => {
execFunctionWithCatchError(onRjected, this.reason, resolve, reject);
});
}
}
})
}
catch(onRjected) {
return this.then(undefined, onRjected);
}
finally(onFinally) {
this.then(
() => {
onFinally();
},
() => {
onFinally();
}
)
}
static resolve(value) {
return new MyPromise(resolve = resolve(value));
}
static reject(reason) {
return new MyPromise(resolve, reject = reject(reason));
}
static all(promises) {
return new MyPromise((resolve, reject) => {
const values = [];
promises.forEach(promise => {
promise.then(res => {
values.push(res);
if (values.length === promises.length) {
resolve(values);
}
},
err => {
reject(err);
});
})
})
}
static allSettled(promises) {
return new MyPromise(resolve => {
const results = [];
promises.forEach(promise => {
promise.then(
res => {
results.push({status: PROMISE_STATUS_FULFILLED, value: res});
if (results.length === promises.length) {
resolve(results);
}
},
err => {
results.push({
status: PROMISE_STATUS_REJECTED, value: err
});
if (results.length === promises.length) {
resolve(results);
}
}
)
})
})
}
static race(promises) {
return new MyPromise((resolve, reject) => {
promises.forEach(promise => {
promise.then(res => {
resolve(res);
}, err => {
reject(err);
})
})
})
}
static any(promises) {
return new MyPromise((resolve, reject) => {
const reasons = [];
promises.forEach(promise => {
promise.then(
res => {
resolve(res);
},
err => {
reasons.push(err);
if (reasons.length === promise.length) {
reject(reasons);
}
}
)
})
})
}
}
const p1 = new MyPromise((resolve, reject) => {
setTimeout(() => {
console.log('---- 1');
resolve(111);
});
}).then(res => {
console.log('p1 res :>>', res);
});
const p2 = new MyPromise((resolve, reject) => {
console.log('---2');
resolve(2);
});
const p3 = new MyPromise((resolve, reject) => {
console.log('---3');
resolve(333);
});
const p4 = new MyPromise((resolve, reject) => {
console.log('---4');
reject(444);
});
MyPromise.all([p2, p3]).then(res => {
console.log('p2 & p3 res :>>', res);
});
MyPromise.all([p2, p4]).then(res => {
console.log('p2&p4 res :>>', res);
}).catch(err => {
console.log('err :..', err);
});
