SOURCE

let STATE = {
    进行中: 'pending',
    成功: 'fulfilled',
    失败: 'rejected',
}

function Mypromise(fn) {
    this.state = STATE['进行中']; // 状态
    this.value = null // 成功的值
    this.error = null // 失败的值
    let onFulfilled = function (value) { // 成功回调函数
        console.log(value)
    }
    let onRejected = function (value) { // 失败回调函数 
        console.log(value)
    }
    let resolve = (value) => { // 执行成功的函数
        if (this.state === STATE['进行中']) {
            onFulfilled(value)
            this.state = STATE['成功']

        }
    }
    let reject = (value) => { // 执行失败的函数
        if (this.state === STATE['进行中']) {
            onRejected(error)
            this.state = STATE['失败']
        }
    }

    fn(resolve, reject)
}

Mypromise.prototype.then = function (onFulfilled, onRejected) {
    console.log(this)
}

let p1 = new Mypromise((resolve, reject) => {
    // console.log(111)
    resolve(222)
    reject(333)
})

p1.then()