wer

class MyPromise  {
    constructor(f) {
        this._reject = null

        let promise = new Promise((resolve, reject) => {
            this._reject = reject
            f(resolve, reject)
        })

        promise.cancel = () => {
            this._reject('Rejected')
        }

        return promise
    }
}

function test() {
    return new MyPromise((resolve, reject) => {
        setTimeout(() => {
            resolve(123)
        }, 1000)
    })
}


let promise = test()
promise
    .then(() => {
        console.log(321)
    })
    .catch(e => {
        console.log(e)
    })

promise.cancel()