promise

time 2m41s

class MyPromise {
    constructor() {
    }
}
/*换成mypromise*/
// const p1 = new Promise((resolve, reject) => {
const p1 = new MyPromise((resolve, reject) => {
    resolve(1);
})
p1.then((res) => {
    console.log(res);
}, err => {
    console.log(err);
})
/*1*/

第一步

time 5m54s

class MyPromise {
    constructor(executor) {
        this.state = 'pending';
        this.value = undefined;
        this.reason = undefined;
        let resolve = (value) => {
            this.state = 'fullFilled';
            this.value = value
        }
        let reject = (reason) => {
            this.state = 'rejected';
            this.reason = reason;
        }
        executor(resolve, reject);
    }
    then(onFullFilled, onRejected) {
        if (this.state === 'fullFilled') {
            onFullFilled(this.value);
        }
        if (this.state === 'rejected') {
            onRejected(this.reason);
        }
    }
}
/*换成mypromise*/
// const p1 = new Promise((resolve, reject) => {
const p1 = new MyPromise((resolve, reject) => {
    resolve(1);
})
p1.then((res) => {
    console.log(res);
}, err => {
    console.log(err);
})
/*1*/

处理异步

time 6m35s

class MyPromise {
    constructor(executor) {
        this.state = 'pending';
        this.value = undefined;
        this.reason = undefined;
        this.onFullFilledCallbacks = [];
        this.onRejectedCallbacks = [];
        let resolve = (value) => {
            this.state = 'fullFilled';
            this.value = value;
            // this.onFullFilledCallbacks.forEach(fn => fn(this.value));
            this.onFullFilledCallbacks.forEach(fn => fn());
        }
        let reject = (reason) => {
            this.state = 'rejected';
            this.reason = reason;
            // this.onRejectedCallbacks.forEach(fn => fn(this.value));
            this.onRejectedCallbacks.forEach(fn => fn());
        }
        executor(resolve, reject);
    }
    then(onFullFilled, onRejected) {
        if (this.state === 'fullFilled') {
            onFullFilled(this.value);
        }
        if (this.state === 'rejected') {
            onRejected(this.reason);
        }
        if (this.state === 'pending') {
            /* this.onFullFilledCallbacks.push(onFullFilled);
             this.onRejectedCallbacks.push(onRejected);*/
            this.onFullFilledCallbacks.push(() => {
                onFullFilled(this.value);
            });
            this.onRejectedCallbacks.push(()=>{
                onRejected(this.reason);
            });
        }
    }
}
/*换成mypromise*/
// const p1 = new Promise((resolve, reject) => {
const p1 = new MyPromise((resolve, reject) => {
    setTimeout(() => {
        resolve(1);
    }, 1000)
})
p1.then((res) => {
    console.log(res);
}, err => {
    console.log(err);
})
p1.then((res) => {
    console.log(res);
}, err => {
    console.log(err);
})
/*1  1*/

处理链式操作

time 10m20s

class MyPromise {
    constructor(executor) {
        this.state = 'pending';
        this.value = undefined;
        this.reason = undefined;
        this.onFullFilledCallbacks = [];
        this.onRejectedCallbacks = [];
        let resolve = (value) => {
            this.state = 'fullFilled';
            this.value = value;
            // this.onFullFilledCallbacks.forEach(fn => fn(this.value));
            this.onFullFilledCallbacks.forEach(fn => fn());
        }
        let reject = (reason) => {
            this.state = 'rejected';
            this.reason = reason;
            // this.onRejectedCallbacks.forEach(fn => fn(this.value));
            this.onRejectedCallbacks.forEach(fn => fn());
        }
        executor(resolve, reject);
    }
    then(onFullFilled, onRejected) {
        /*因为判断是同步执行的*/
        const p2 = new MyPromise((resolve, reject) => {
            let x;
            if (this.state === 'fullFilled') {
                x = onFullFilled(this.value);
                // console.log('165:'+x)
                resolve(x);
            }
            if (this.state === 'rejected') {
                x = onRejected(this.reason);
                resolve(x);
            }
            if (this.state === 'pending') {
                /* this.onFullFilledCallbacks.push(onFullFilled);
                 this.onRejectedCallbacks.push(onRejected);*/
                this.onFullFilledCallbacks.push(() => {
                   x= onFullFilled(this.value);
                    resolve(x);
                });
                this.onRejectedCallbacks.push(() => {
                   x= onRejected(this.reason);
                    resolve(x);
                });
            }
        })
        return p2;
    }
}
/*换成mypromise*/
// const p1 = new Promise((resolve, reject) => {
const p1 = new MyPromise((resolve, reject) => {
    // setTimeout(() => {
    //     resolve(1);
    reject(1);
    // }, 1000)
})
const p2 = p1.then((res) => {
    // console.log(res);
    return res + 1;
}, err => {
    // console.log(err)
    return err + 2;
})
p2.then(res => {
    console.log(res,'success');
}, err => {
    console.log(err,'error');
})
/*3 success*/

处理new MyPromise

time 16m35s

time 34m06s