getList.js

const getList = (employeeUID) => {
    let result = {};
    const ref = database.ref('employee_works').child(employeeUID).orderByValue().equalTo(true);
    return new Promise((resolve, reject) => {
        ref.once('value')
            .then(workUIDs => {
                if (workUIDs.val()) {
                    Object.keys(workUIDs.val()).map(item => {
                        database.ref('works').child(item).once('value')
                            .then(workDetails => result[item] = workDetails.val())
                            .catch(e => reject('Erro ao capturar dados: ', e))
                    })
                    return resolve(console.log('Resultado: ', result))
                }
            })
            .catch(e => reject('Nenhuma obra relacionada a este funcionário', e))
    })
}

Retornando o objeto estruturado:

return Promise.all(PromiseStack).then(PromiseValues => result)