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/**
 * 请始终使用catch
 * 请始终使用catch
 * 请始终使用catch
 */


class PromiseDone {

    promise = null
    value = undefined

    nextId = 0
    nextMap = {}
    constructor(promise) {
        this.promise = promise
    }

    done(cb) {
        this.done = cb
    }

    then(resolve, reject) {
        return this.promise.then(value => {
            if (!resolve) return

            const returnVal = resolve(value)
            if (returnVal) {
                this.value = returnVal

                this.nextMap[this.nextId++] = returnVal
                this.exec()
            }


            console.log(this.nextMap)
            return this.then
        }, err => {
            if (!reject) return

            const returnVal = resolve(value)
            if (returnVal) {
                this.value = returnVal

                this.nextMap[this.nextId++] = returnVal
                this.exec()
            }

            console.log(this.nextMap)
            return this.then
        })
    }

    exec() {

    }
}


{
    const p = new PromiseDone(new Promise(r => r(1)))
    p.then(v => {
        console.log('v1', v)
        return 2
    }).then(v => {
        console.log('v2', v)
    })

    p.then(v => {
        console.log('v3', v)
    }).then(v => {
        return new Promise(r => {
            setTimeout(r, 1000, 100)
        })
    }).then(v => {
        console.log('v33', v)
    })

    p.done(() => {
        console.log(1)
    })
}


{
    const p = new Promise(r => r(1))
    p.then(v => {
        console.log(v)
        return 2
    }).then(v => {
        console.log(v)
    })

    p.then(v => {
        console.log(v)
        return v
    }).then(v => {
        console.log(v)
    })
}