Обработка ошибок с помощью Node.js, Async и Formableable

Ответ 1

Я извлечу проверку формы в функцию:

var form = new formidable.IncomingForm();

function check(name, cb, err){
 return new Promise((res,rej)=>{
  form.on('field', function (n, val) {
        if( n !== name) return;
        if( cb(val) ){
          res(val);
        }else{
          rej(err);
       }
   });
 });
}

form.parse( req );

Итак, теперь мы можем реализовать проверки и использовать Promise.all, чтобы суммировать их:

 Promise.all(
   check("username", val => val.length > 4,"username isnt valid"),
   check("password", val => true,"we need a password")
 ).then(_=>res.json({status:200}))
  .catch(err => res.json({err}));

Если не все все параметры переданы, это будет бесконечно ждать. Итак, прекратите действие, если оно было закончено:

const ended = new Promise((_,rej)=>form.on("end",()=>rej("params required"));

Promise.race(
 ended,
  Promise.all(
   check("username", val => val.length > 4,"username isnt valid"),
   check("password", val => true,"we need a password")
  )
).then(_=>res.json({status:200}))
 .catch(err => res.json({err}));

Таким образом, мы можем создать хороший поток данных. например:.

const login = Promise.all(
  //usable as one liners
 check("username", val => val.length >= 8,"username invalid"),
 //or more extensible
 check("password", val =>{
   if( val.length < 8 ) return false;
   //other checks
   console.log(password);
   return true;
 },"password invalid")
//the field values are resolved by the promises so we can summarize them below 
).then(([username,password])=>
   //a random (maybe async) call to evaluate the credentials
  checkAgainstDB(username,password)
  //we can directly fail here, err is  "password invalid" or "username invalid"
).catch(err =>res.json({error:"login failed",details:err}));

 //another parameter can be extra handled    
const data = check("something",val => val.length);

//we need to summarize all the possible paths (login /data in this case) to one that generates the result
Promise.race(
 //here we join them together
 Promise.all(login,data)
   .then((l,d)=>res.json(whatever),
 //and we use the ended promise ( from above ) to end the whole thing
 ended
  //and at last the errors that can occur if the response ended or that have not been canceled early
).catch(e => res.json(e));

Ответ 2

var form = new formidable.IncomingForm();

async1.series([
    function (callback) {
        form.parse(req);

        form.on('field', function (name, val) {
            if (!name || !val) {
              // the moment callback is called with an error, async will stop execution of any of the steps
              // in the series and execute the function provided as the last argument
              // idimoatic node, when calling the callback with instance of Error
              return callback(new Error('InvalidParams'));
            }

            /**
             * This is from async documentation: https://caolan.github.io/async/docs.html#series
             * Run the functions in the tasks collection in series, each one running once the previous function 
             * has completed. If any functions in the series pass an error to its callback, no more functions are 
             * run, and callback is immediately called with the value of the error. Otherwise, callback receives 
             * an array of results when tasks have completed.
             */
        });

        form.on('fileBegin', function (name, file) {
            if (file.name !== "") {
                file.path = __dirname + '/upload/' + file.name;
            }
        });

        form.on('end', function () {
          // call callback with null to specify there no error
          // if there are some results, call it like callback(null, results);
          return callback(null);
        });

        // if you call the callback immediately after registering event handlers for on('field') etc,
        // there will be no time for those events to be triggered, by that time, this function will be 
        // done executing.
        //callback();
    },
    function (callback) {
        form.on('file', function (name, file) {
            try {
                // Do something with the file using the fields retrieved from first async method
            }
            catch (err) {
                logger.info(err);
                return callback(err);
            }
        });

        // This should also not be called immediately
        //callback();
    }
], function (err) {
    //the upload failed, there is nothing we can do, send a 500

    if (err === "uploadFailed") {
        return res.send(500);
    }

    if (err.message === 'InvalidParams') {
      // This will be immediately returned to the user.
      return res.sendStatus(400);
    }

    if (err) {
      // I'm not sure if this was just for the example, but if not, you should not be throwing an error
      // at run time. 
        throw err;
    }
    return res.status(200);

});

Ответ 3

Я предполагаю, что это хорошее место для проверки, так как это когда появляются поля:

form.on('field', function (name, val) {
    //if values are null
    if (!name || !val) {
        //pass the callback an error 
        return callback("Values are null")
    }
    // Get the fields
});

Пожалуйста, дайте мне знать, если это поможет.