promise_example1.js

/**
 * promise object
 */

function getUserWithId(id) {
    return new Promise((resolve, reject) => {
        // Look for a user with id in the database
        User.find({_id: id}, (user, err) => {
            if(err) return reject(err);

            // on success
            resolve(user); // from pending --> resolved
        });
    });
}
    
/**
 * 
 */
getUserWithId(someId)
    .then(user => {
        // we got a successfull object, send it back to the user or
        // something like that.
    })
    .catch(ex => {
        // send or throw an error   
    });