function MyPromise(exector) {
let self = this;
self.value = undefined;// 存储成功状态下的值
self.reason = undefined;// 存储失败状态下的原因
self.status = 'pending';// 存储promise的状态
self.resCallback = [];// 存储成功的回调函数
self.rejCallback = [];// 存储失败的回调函数
function resolve(value) {
setTimeout(() => {
if (self.status === 'pending') {
self.status = 'resolved'
self.value = value;
self.resCallback.forEach(item => {
item && item(self.value)
})
}
});
}
function reject(reason) {
setTimeout(() => {
if (self.status === 'pending') {
self.status = 'rejected'
self.reason = reason;
self.rejCallback.forEach(item => {
item && item(self.reason);
})
}
});
}
try {
exector(resolve, reject)
} catch (error) {
reject(error)
}
}
MyPromise.prototype.then = function (res, rej) {
let self = this;
return new MyPromise(function (res2, rej2) {
if (self.status === 'resolved') {
// 第二个then的回调函数参数是由第一个then的回调函数的执行结果赋予的
try {
let value = res(self.value);
res2(value)
} catch (error) {
rej2(error)
}
}
if (self.status === 'rejected') {
try {
let reason = rej(self.reason);
// 上一个失败回调 执行没出现错误
// 就需要让下一个then的成功回调函数执行
res2(reason)
} catch (error) {
rej2(error)
}
}
if (self.status === 'pending') {
// self.resCallback.push(res);
// self.rejCallback.push(rej);
self.resCallback.push(function (value) {
try {
let val = res(value);
res2(val);
} catch (error) {
rej2(error)
}
})
self.rejCallback.push(function (reason) {
try {
let val = rej(reason);
res2(val);
} catch (error) {
rej2(error)
}
})
}
})
}
MyPromise.all = function (ary) {
// ary 中都是MyPromise实例
return new MyPromise(function (res, rej) {
let done = gen(ary.length, res);
ary.forEach((item, index) => {
item.then((data) => {
done(index, data)
}, rej)
})
})
}
function gen(length, res) {
let values = [];
let count = 0;
return function (index, value) {
values[index] = value;
if (++count == length) {
res(values)
}
}
}
let myp1 = new MyPromise((res, rej) => {
setTimeout(() => {
res(666)
}, 2000);
})
let myp2 = new MyPromise((res, rej) => {
setTimeout(() => {
res(999)
}, 4000);
})
MyPromise.all([myp1, myp2]).then((data) => {
console.log(data)
}, (err) => {
console.log(err)
})
