回调函数如何改成promise并且不影响原来的业务逻辑

// old
const getData = callback => {
    setTimeout(() => {
        const number = Math.random();
        callback(number);
    }, 5000);
}


// new
const getData = callback => {
    let promiseReject;
    const promise = new Promise(reject => promiseReject = reject);
    setTimeout(() => {
        const number = Math.random();
        promiseReject(number);
        callback && callback(number);
    }, 5000);
    return promise
}