复习之前的

catch方法

time 18m55s

    catch(onRejected) {
        return this.then(null, onRejected);
    }

resolve方法

time 20m03s
time 30
time 43m

测试方法

const p1 = new MyPromise((resolve, reject) => {
    setTimeout(() => {
        reject('1000');
    }, 3000)
})
MyPromise.resolve(p1)
    .then(res => console.log(res, 'success')
        , err => console.log(err, 'fail')
    )

1000 fail

/**
 * 判断值是否是promise对象，thanable对象
 * @param value 参数，在这里是回调函数，比如promise.resolve的参数，可能是函数，
 * 可能是promise对象
 * @returns {boolean} 是否是promise对象，thenable对象
 */
const isPromsie = (value) => typeof value.then === "function";

   static resolve(value) {
        if (isPromsie(value)) {
            return value;
        } else {
            return new MyPromise((resolve, reject) => {
                resolve(value)
            })
        }
    }

当时promise对象时，返回promise对象value，当不是时返回经过包装的promise对象

const p1 = new MyPromise((resolve, reject) => {
    setTimeout(() => {
        reject(new MyPromise((resolve, reject) => {
            setTimeout(()=>{
                reject('1000');
            },3000)
        }));
    }, 3000)
})
MyPromise.resolve(p1)
    .then(res => console.log(res, 'success')
        , err => console.log(err, 'fail')
    )

    static resolve(value) {
        return new MyPromise((resolve, reject) => {
            resolve(value)
        })
    }

把isPromsie放到resolve中

        let resolve = (value) => {
            if (this.state === 'pending') {
                /*time 43m*/
                if (isPromsie(value)) {
                    /*递归调用，继续resolve，如果是reject走reject
                    * value是promise，但最终还是得resolve或reject，所以得用then
                    * 运行，为了运行resolve、或者reject，通过then取出promise对象value
                    * 中的值，再进行resolve或者reject，reject是不能运行一个promise对象的*/
                    value.then(data => resolve(data), err => reject(err));
                } else {
                    this.state = 'fullFilled';
                    this.value = value;
                    // this.onFullFilledCallbacks.forEach(fn => fn(this.value));
                    this.onFullFilledCallbacks.forEach(fn => fn());
                }
            }
        }

finally

time 49m