SOURCE

class Promise {
    constructor (handelFunc) {
        this.status = 'pedding'
        this.vallue = ''
        this.fulFilledList = []
        this.rejectList = []
        console.log(1)
        handelFunc(this.triggeResolve.bind(this), this.triggeReject.bind(this))
    }
    
    then (onFulFilled, onReject) {
        console.log(3)
        const {value, status} = this
        return new Promise((onNextFulFilled, onNextReject) => {
            console.log(5)
            switch(status) {
                case 'pedding':
                    this.fulFilledList.push(onFulFilled)
                    this.rejectList.push(onReject)
                break;
            }
        })

    }
    catch () {

    }

    triggeFulFilled () {
        this.fulFilledList.forEach(item => item())
        this.fulFilledList = []
    }
    triggeResolve (val) {
        console.log(2)
        setTimeout(() => {
            console.log(4)
            if (this.status != 'pedding') return
            if (val instanceof Promise) {
                val.then(
                    value => {},
                    err => {}
                )
            } else {
                this.status = 'fulFilled'
                this.value = val
                this.triggeFulFilled()
            }
        }, 0)
    }
    triggeReject () {
        
    }

    static resolve () {

    }
    static reject () {

    }
    static all () {

    }
    static reace () {

    }
}


let promise = new Promise((resolve, reject) => {
    resolve('1234')
})

promise.then((val) => {
    console.log(val)
})