I've found several examples on S/O and otherwise, but they don't seem to be helping me.
I'm creating a private module in node that takes in a csv and converts it into a json object. It is properly outputting the correct value onto the command line, but the object itself is undefined.
exports.csvToJSON = function(file, callback) {
converter.fromFile(file, function(err, result) {
if (err) {
console.log('error: ', error)
} else {
return result;
callback(err, result);
}
});
console.log(callback)
}
I'm currently using the csvtojson module and have tried other similar packages. Articles I've referenced:
Function Returns undefined object
Why does this callback return undefined?
Why is function return value undefined when returned in a loop? (although not entirely relevant as this is not a loop function)
Callback returning undefined
I'm unsure if I'm just not understanding the callback correctly, but even if I console.log(result.type), it returns back undefined with or without the callback. I've also tried defining the callback like so:
exports.csvToJSON = function(file, callback) {
csvtojson().fromFile(file, function(err, result) {
if (err) {
console.log('error: ', error)
}
return result;
callback(result);
});
}
Here's an example of the console output:
Mirandas-MacBook-Pro:zendesktool mirandashort$ node ./controllers/update.js
[ { ticket:
{ ids: '3280805',
requester_email: 'miranda#barkbox.com',
status: 'pending',
comment: [Object],
subject: 'sup dog',
custom_fields: [Object],
add_tags: 'update_via_csv, dogs_are_cool, sup' } } ] undefined
Right now, since my other functions are dependent on this working, I'm only calling it in the file with exports.csvToJSON('update2.csv') where update2.csv is an actual file. Eventually this will be called inside another function in which I will be utilizing async, but I need this to work first. Additionally, that output seems to be linked to console.log(err) when called by the second code block example, which I'm not to sure why.
Or if there's a way to do this altogether without csvtojson, that's fine too. The only requirement be that a file in csv format can be returned as an object array.
Got it. I just used waterfall to put the two individual modeles together:
exports.csvToJSON = function(file, callback) {
csvtojson().fromFile(file, function(err, result) {
if (err) {
console.log(err);
} else {
callback(null, result[0]);
}
});
}
exports.zdUpdateMany = function(data, callback) {
credentials.config.tickets.updateMany(3280805, data, function(err, result) {
if (err) {
console.log(err);
} else {
callback(false, result);
}
});
}
// function to update tickets
exports.processUpdate = function(file, callback) {
async.waterfall([
async.apply(exports.csvToJSON, file),
exports.zdUpdateMany
], function(err, result) {
if (err) {
console.log(err);
} else {
console.log(result);
}
callback(err, result);
});
}
Related
I need to save to db inside an async waterfall series.
I've tried to integrate these two function after the clean function
function connectDb(next) {
pool.getConnection(function(err, connection) {
if (err) console.log(err);
conn = connection;
}, next);
},
function saveDb(next) {
let sql = "UPDATE media SET media_url = ? WHERE media_url = ?";
conn.query(sql, [dstKey, srcKey], function (error, results, fields) {
if (error) {
conn.release();
console.log(error);
}else{
console.log("media db updated");
}
}, next)
}
The problem is that these two functions block the code execution. How can I integrate it in the function below? I've tried to wrap the function in promise but it is also not working.
async.waterfall([
function download(next) {
s3.getObject({
//param
},
next);
},
function transform(response, next) {
resizeMedia(response.Body ).then( ( file ) => { next();} ).catch( (err) => { reject(err) } ); }
},
function upload(next) {
var fileData = fs.createReadStream('/tmp/'+dstKey);
if (isVideo ) { var ContentType = 'video/mp4' }
if (isAudio ) { var ContentType = 'audio/mp3' }
s3.putObject({
//param
},
next);
},
function clean(next) {
// Stream the transformed image to a different S3 bucket.
fs.unlinkSync('/tmp/'+dstKey);
s3.deleteObject({
//param
},
next);
}
], function (err) {
if (err) {
console.error('Error');
callback(null, "Error");
return;
} else {
console.log('Success');
callback(null, "Done");
return;
}
callback(null, "Done");
return;
}
);
The purpose of async waterflow is to block the waterfall until the callback is called.
P.S. Usually you should not create a new db connection each time. The connection should be done once when the application start and get used whenever you need.
I highly recommend you to use knex.js instead, it return promises by default and if you like to use it inside async waterfall (and wait for resolve) you can call .asCallback.
I've found the problem, if someone fall into the same issue here my solution:
If a waterfall function has a response, this response is automatically added as first argument in the next function. In my code the mistake was simple (after night's sleep), the s3.deleteObject and s3.putObject has response, this response need to be setted as first argument and the callback as last, as you say I've used only the callback as argument (next) and this broke my code.
[...]
function upload(next) {
s3.putObject({
//param
},
next);
},
function clean(response, next) { // response in arguments
s3.deleteObject({
//param
},
next);
}
[...]
From my Model, I fetch some articles from a MySQL database for a user.
Model
var mysql = require('mysql');
var db = mysql.createPool({
host: 'localhost',
user: 'sampleUser',
password: '',
database: 'sampleDB'
});
fetchArticles: function (user, callback) {
var params = [user.userId];
var query = `SELECT * FROM articles WHERE userId = ? LOCK IN SHARE MODE`;
db.getConnection(function (err, connection) {
if (err) {
throw err;
}
connection.beginTransaction(function (err) {
if (err) {
throw err;
}
return connection.query(query, params, function (err, result) {
if (err) {
connection.rollback(function () {
throw err;
});
}
//console.log(result);
});
});
});
}
This is working and the function fetches the result needed. But it's not returning the result to the controller function (I am returning it but I'm not able to fetch it in the controller function. I guess, I did something wrong here).
When I did console.log(result) this is what I got.
[ RowDataPacket {
status: 'New',
article_code: 13362,
created_date: 2017-10-22T00:30:00.000Z,
type: 'ebook'} ]
My controller function looks like this:
var Articles = require('../models/Articles');
exports.getArticle = function (req, res) {
var articleId = req.body.articleId;
var article = {
userId: userId
};
Articles.fetchArticles(article, function (err, rows) {
if (err) {
res.json({ success: false, message: 'no data found' });
}
else {
res.json({ success: true, articles: rows });
}
});
};
Can anyone help me figure out what mistakes I made here?
I'm pretty new to nodejs. Thanks!
The simple answer is that you're not calling the callback function, anywhere.
Here's the adjusted code:
fetchArticles: function (user, callback) {
var params = [user.userId];
var query = `SELECT * FROM articles WHERE userId = ? LOCK IN SHARE MODE`;
db.getConnection(function (err, connection) {
if (err) {
// An error. Ensure `callback` gets called with the error argument.
return callback(err);
}
connection.beginTransaction(function (err) {
if (err) {
// An error. Ensure `callback` gets called with the error argument.
return callback(err);
}
return connection.query(query, params, function (err, result) {
if (err) {
// An error.
// Rollback
connection.rollback(function () {
// Once the rollback finished, ensure `callback` gets called
// with the error argument.
return callback(err);
});
} else {
// Query success. Call `callback` with results and `null` for error.
//console.log(result);
return callback(null, result);
}
});
});
});
}
There's no point in throwing errors inside the callbacks on the connection methods, since these functions are async.
Ensure you pass the error to the callback instead, and stop execution (using the return statement).
One more thing, without knowing the full requirements of this:
I'm not sure you need transactions for just fetching data from the database, without modifying it; so you can just do the query() and skip on using any beginTransaction(), rollback() and commit() calls.
I would like to analyze a JSON file I dynamically create with Watson's tone analyzer. I would like it to read the file, then analyze it.
How can I make the tone_analyzer.tone method read the file? Thank you.
app.get('/results', function(req, res) {
// This is the json file I want to analyze
fs.readFile('./output.json', null, cb);
function cb() {
tone_analyzer.tone({
// How can I pass the file here?
text: ''
},
function(err, tone) {
if (err)
console.log(err);
else
console.log(JSON.stringify(tone, null, 2));
});
console.log('Finished reading file.')
}
res.render('results');
})
Your callback is missing a couple of arguments (error, data) (see the node fs documentation for more info). Data is the content of your file and would go where you are sending the text.
Try something like this:
app.get('/results', function(req, res) {
// This is the json file I want to analyze
fs.readFile('./output.json', 'utf8', cb);
function cb(error, data) {
if (error) throw error;
tone_analyzer.tone({
// How can I pass the file here?
text: data
},
function(err, tone) {
if (err)
console.log(err);
else
console.log(JSON.stringify(tone, null, 2));
});
console.log('Finished reading file.')
}
res.render('results');
})
Thanks to user Aldo Sanchez for his tip. I converted the input into JSON first since fs was returning it in the form of buffer data. Also, I made it search for the specific value in the key/value pair and return that content, instead of returning the whole string. This can be directly inputted to Watson's tone analyzer.
var data = fs.readFileSync('./output.json', null);
JSON.parse(data, function(key, value) {
if (key == "message") {
cb(value);
}
function cb(value, err) {
if (err) throw err;
tone_analyzer.tone({
text: value
},
function(err, tone) {
if (err)
console.log(err);
else
console.log(tone);
});
}
console.log('Finished reading file.')
});
why I cannot get results?
var sql_data = connection.query(sql, function(error, results, fields) {
if(error) {
console.log(error);
return;
}
var rows = JSON.parse(JSON.stringify(results[0]));
console.log(rows);
});
console.log(rows);
fiirst console.log is ok, display object,
but second says:
ReferenceError: rows is not defined
what is wrong?..
You shouldn't assign asynchronous function to a variable just like you do in first line of your code. You just call it and perform operations on the result with use of callback methods (which in this case is function(error, results, fields). Your code should look like below
connection.query(sql, function(error, results, fields) {
if(error) {
console.log(error);
return;
}
var rows = JSON.parse(JSON.stringify(results[0]));
// here you can access rows
console.log(rows);
});
// here it will be undefined
console.log(rows);
The rows variable in second console.log will be undefined because it was defined in different scope. Even if you would do var rows above the connection.query, it would still be undefined, because you assign it's value inside asynchronous function's callback. You need to read more about this kind of operations.
You should use then Promise if you want to get the query result. I prefere it to be onest. The Promise runs the command async.
function getDomain() {
return result = await dbQuery('SELECT name FROM virtual_domains ORDER BY id;');
}
// * Important promise function
function dbQuery(databaseQuery) {
return new Promise(data => {
db.query(databaseQuery, function (error, result) { // change db->connection for your code
if (error) {
console.log(error);
throw error;
}
try {
console.log(result);
data(result);
} catch (error) {
data({});
throw error;
}
});
});
}
I'm trying to parse XML to JSON in Node. I'm using xml2js. I'd like to incorporate Lodash to loop through each number in an array and use the corresponding url to convert the XML to JSON. When I use the code below, I get a Non-whitespace before first tag error. Any idea what I'm doing wrong?
const no = [78787878,78787879, 787878780];
_.forEach(no, https.get('https://tsdrapi.uspto.gov/ts/cd/casestatus/'+no+'/info.xml', function (res) {
res.on('data', function (chunk) {
response_data += chunk;
});
res.on('end', function () {
parser.parseString(response_data, function (err, result) {
if (err) {
console.log('Got error: ' + err.message);
} else {
console.log(util.inspect(result, false, null));
}
});
});
res.on('error', function (err) {
console.log('Got error: ' + err.message);
});
}));
Honestly the forEach helper in LoDash is kind of silly. forEach is a prototype method of any Array instance. One problem is that these functional helpers are not designed to handle async flow control.
While there are a dozen ways to handle flow control the easiest would probably be to use caolan/async module's map() method.
You're code would look something like:
var no = [78787878,78787879, 787878780];
async.map(no, function(cb) {
https.get('https://tsdrapi.uspto.gov/ts/cd/casestatus/'+no+'/info.xml', function (res) {
var response_data = '';
res.on('data', function (chunk) {
response_data += chunk;
});
res.on('end', function () {
parser.parseString(response_data, function (err, result) {
if (err) {
cb(err);
} else {
cb(null, result);
}
});
});
res.on('error', cb);
})
}, function(err, results) {
if(err) {
console.log("Error occured: ", err);
}
else {
console.log("Results(array): ", results);
}
});
The difference here is that async maps the array to a function with a callback. This way you can gather the response from each request into an array and fire a callback when each request has responded. If one of them error's out the process stops and fires the final callback where the error is logged(or you can write logic to handle another way).