I am using oracledb with node and fetching data from it asynchronously. For the sake of ease, I have implemented it using separate files like below -
config.js -
module.exports = {
user : "user",
password : "password",
connectString : "*connstring*" ,
deliveredQuery: " SELECT COUNT (DISTINCT order_num) AS Cnt from orders where department = 'HR'
};
query2.js :
module.exports = function(callback) {//pass callback function and return with this
var oracledb = require('oracledb');
var dbConfig = require('./config.js');
this.queryDB = function(query,callback) {
oracledb.getConnection({
user: dbConfig.user,
password: dbConfig.password,
connectString: dbConfig.connectString,
deliveredQuery: dbConfig.deliveredQuery
}, function(err, connection) {
if (err) {
console.error(err.message);
return callback(err);
}
connection.execute(query, function(err, result) {
if (err) {
console.error(err.message);
doRelease(connection);
return;
}
//console.log(result.metaData);
//console.log(JSON.parse(result.rows[0][0]));
doRelease(connection);
return callback(null, JSON.parse(result.rows[0][0]))
});
});
function doRelease(connection) {
connection.release(function(err) {
if (err) {
console.error(err.message);
return callback(err);
}
});
}
};
};
serv_ontime.js :
var dbConfig = require('./config.js');
var res = require('./query2.js')();
var onTime_query = dbConfig.onTime_query;
module.exports = queryDB(onTime_query, function(err, callback){ });
index.js :
var res = require('./serv_ontime.js');
console.log("The result is= "+ res);
Now, When I am doing - node index.js from my cmd then I am getting the output as [object Object]. I suppose it is because the call is happening asynchronously. But if you see in the file query2.js , I am returning the value after parsing(using JSON.parse) but still the value I am getting in the index.js file is not the parsed one. How can I parse the value in index.js? I have already tried JSON.parse but it doesn`t work.
You are getting output as [object Object] because you are doing + with a String('The result is= '), So js engine tries to convert the Object to a String. To view it as an Object, do log it separately or log with comma separated,
console.log('The result is= ', res); (or)
console.log(res); // or console.dir(res)
Or you can get String version of it, by doing JSON.stringify(res)
console.log('The result is= ', JSON.stringify(res));
In serv_ontime.js you are exporting result of queryDB witch indeed is undefined. Ty this:
serv_ontime.js
var dbConfig = require('./config.js');
var res = require('./query2.js')();
var onTime_query = dbConfig.onTime_query;
module.exports = function (callback) {
queryDB(onTime_query, callback)
};
index.js
var serv_ontime = require('./serv_ontime.js');
serv_ontime(function(error, res) {
console.log("The error is= ", error);
console.log("The result is= ", res);
});
Related
I'm learning Node.js and I'm just starting to work with some MySQL connections. I have a function which is supposed to get a set of rows from the database. However I can't get the value from it.
//connect.js
var mysql = require('mysql');
module.exports = {
world : function () {
var conn = mysql.createConnection({
host : '',
user : 'root',
password : '',
database : ''
});
conn.connect(function(err){
if(err) throw err;
});
conn.query('SELECT * FROM `room` WHERE 1', function(err, result, fields){
if(err) throw err;
var id = JSON.stringify(result[0].id);
var name = JSON.stringify(result[0].name);
var time = JSON.stringify(result[0].time);
return time;
});
conn.end(function(err){
if(err) throw err;
})
}
};
And I try to get the value by this program:
//show.js
var hello = require('./connect');
console.log(hello.world());
The result like this:
$ node show
undefined
So how should I get the value?
You cannot just return an asynchronous value inside your connect.js.
To return this value time, you have to pass by a callback function, or a promise.
This is an example of a callback :
//connect.js
var mysql = require('mysql');
module.exports = {
world : function (callback) { // Now world method takes a callback function parameter
var conn = mysql.createConnection({
host : '',
user : 'root',
password : '',
database : ''
});
conn.connect(function(err){
if(err) callback(err, null); // Callback an error
});
conn.query('SELECT * FROM `room` WHERE 1', function(err, result, fields){
if(err) callback(err, null); // Callback an error
else {
var id = JSON.stringify(result[0].id);
var name = JSON.stringify(result[0].name);
var time = JSON.stringify(result[0].time);
callback(null, time); // callback your response here
}
});
conn.end(function(err){
if(err) callback(err, null); // Callback an error
})
}
};
And this is how you can get the response
//show.js
var hello = require('./connect');
hello.world(function(err, response) {
if (err) throw err;
console.log(response);
});
I suggest you to learn more about Javascript asynchronous
Hope it helps.
I am reading files from ftp using the code below.
var JSFtp = require("jsftp");
var config = require('./config.json');
var FtpService = function () {};
// Connect to FTP
var Ftp = new JSFtp({
host: config.ftp.host,
port: config.ftp.port,
user: config.ftp.user,
pass: config.ftp.pass
});
FtpService.prototype.getFTPDirectoryFiles = function (callback) {
Ftp.list(config.ftp.FilePath, function(err, res) {
if(err){
console.log('File Listing Failed', err);
callback(null,err);
return;
}
else{
console.log(res);
callback(null,res);
}
});
};
FtpService.prototype.closeFtp = function () {
console.log('Disconnect to FTP');
};
module.exports = new FtpService();
Now i include this ftp service js file in my index.js as
var ftp = require('./ftpservice.js');
ftpfiles = ftp.getFTPDirectoryFiles();
console.log(ftpfiles);
getFTPDirectoryFiles returns the list of file. But if i call it via index.js i get undefined ftpfiles. This is because of the asynchronous nature of node js.
so i thought of adding callback but
I am getting the error Callback is not defined in function FtpService.prototype.getFTPDirectoryFiles
In this line:
ftpfiles = ftp.getFTPDirectoryFiles()
you are not passing the callback that that function requires and are trying to use a return value that the function does not return.
You need to do something like this:
var ftp = require('./ftpservice.js');
ftp.getFTPDirectoryFiles(function(err, ftpfiles) {
if (err) {
console.log(err);
} else {
console.log(ftpfiles);
}
});
You need to pass a callbackfunction in your function getFTPDirectoryFiles();
var ftp = require('./ftpservice.js');
var ftpFiles;
function setFtpFiles(err, res) {
if (err) throw err;
ftpFiles = res; // to use "ftpFiles" variable later
console.log(res);
}
ftp.getFTPDirectoryFiles(setFtpFiles);
1 Don't change args order to call callback. (replace callback(null,err); and callback(null,res); by callback(err,res);)
2 You need define a specifc function (your callaback) an give it to ftp.getFTPDirectoryFiles().
var JSFtp = require("jsftp");
var config = require('./config.json');
var FtpService = function () {};
// Connect to FTP
var Ftp = new JSFtp({
host: config.ftp.host,
port: config.ftp.port,
user: config.ftp.user,
pass: config.ftp.pass
});
FtpService.prototype.getFTPDirectoryFiles = function (callback) {
Ftp.list(config.ftp.FilePath, function(err, res) {
if(err){
console.log('File Listing Failed', err);
callback(err, res);
return;
}
else{
console.log(res);
callback(err, res);
}
});
};
FtpService.prototype.getFTPDirectoryFilesSimplify = function (callback) {
// no console.log, but very more simple !
Ftp.list(config.ftp.FilePath, callback);
};
FtpService.prototype.closeFtp = function () {
console.log('Disconnect to FTP');
};
and then :
var ftp = require('./ftpservice.js');
ftpfiles = ftp.getFTPDirectoryFiles(function(err,res){
// do your specifc job here using err and res
});
console.log(ftpfiles);
I have a function that downloads the user input(currently named app.json) from browser(client) to the server
function downloadUpdate(callback) {
//Using formidable node package for downloading user input to server
var form = new formidable.IncomingForm();
form.on('fileBegin', function(name, file) {
file.path = "app.json";
});
form.parse(req, function(err, fields, files) {
res.writeHead(200, {
'content-type': 'text/plain'
});
res.write('received upload:\n\n');
res.end(util.inspect({
fields: fields,
files: files
}));
});
form.on('end', function() {
callback(null);
});
}
I have another function that takes the file downloaded above and converts it into required format(final.json) something like this.
function UpdateCode(callback) {
var obj = fs.readFileSync('app.json', 'utf8');
console.log(abc); //Im getting undefined here
var object = JSON.parse(obj);
var data2 = [];
for (var j = 0; j < object.length; j++) {
if (object[j].value == `${abc}`) {
data2.push(object[j]);
}
}
console.log(data2);
fs.appendFile('final.json', JSON.stringify(data2), function(err) {
if (err) throw err;
console.log('Saved!');
callback(null);
});
}
I used async series function to make them run in an order like this
async.series([
downloadUpload,
UpdateCode
], function(err, result) {
if (err) throw err;
else {
console.log(result);
}
});
All of this code is inside a post request. I'm getting abc from the server
app.post('/', function(req,res){
var abc = req.body.abc;
console.log(abc); //I'm getting abc here
function downloadfile(callback){
//here goes the downloadfile definition
}
function UpdateCode(){
//upload code function
}
//now i call async.series method
async.series([
downloadUpload,
UpdateCode
], function(err, result) {
if (err) throw err;
else {
console.log(result);
}
});
});
the thing is the value of abc is not going to function UploadCode and when I console log abc, I get undefined. Where am I going wrong?
I am trying to get the name and created date of the files. In the code below it throws error when I call the api. It is reading the directory and printing all the file names but it's not sending back to callback. Any idea what is implemented wrong?
service.js
var fs = require('fs');
var path = require('path');
var async = require('async');
var currentDate = new Date();
var objToReturn = [];
var logsDirectory = './logs'
function readDirectory(env, callback) {
fs.readdir(logsDirectory + '/' + env, function(err, files) {
// loop through each file
async.eachSeries(files, function(file, done) {
var dirPath = logsDirectory + '/' + env;
var filePath = path.join(dirPath, file);
var fileInfo = {};
fs.stat(filePath, function(err, stats) {
if (err) {
console.info("File doesn't exist");
} else {
fileInfo.fileDate = stats.birthtime;
fileInfo.filename = file;
objToReturn.push(fileInfo);
done();
}
});
});
},
function(err) {
if (err) {
console.info('error', err);
return;
}
// when you're done reading all the files, do something...
console.log('before Callback', objToReturn);
callback(objToReturn);
});
}
exports.readDirectory = readDirectory;
app.js
var stDirectory = require('./app/serverfiles/stDir');
app.get('/getAllFiles',function(req,res){
var env = req.query.env
console.log('printing',env);
stDirectory.readDirectory(env,function(files){
res.json(files);
console.log('Api files',files);
});
});
There are a few issues:
instead of passing the "final" handler to async.eachSeries(), you're passing it to fs.readdir(), so callback will never get called;
you're declaring objToReturn outside of the function, which isn't a good idea because multiple requests could be handled in parallel;
you're not handling any errors properly;
you should really use the Node.js callback idiom of calling callbacks with two arguments, the first being errors (if there are any) and the second being the result of the asynchronous operation.
The code below should fix these issues:
function readDirectory(env, callback) {
let objToReturn = [];
fs.readdir(
logsDirectory + "/" + env,
function(err, files) {
if (err) return callback(err);
// loop through each file
async.eachSeries(files, function(file, done) {
var dirPath = logsDirectory + "/" + env;
var filePath = path.join(dirPath, file);
var fileInfo = {};
fs.stat(filePath, function(err, stats) {
if (err) {
console.info("File doesn't exist");
return done(err);
} else {
fileInfo.fileDate = stats.birthtime;
fileInfo.filename = file;
objToReturn.push(fileInfo);
done();
}
});
}, function(err) {
if (err) {
console.info("error", err);
return callback(err);
}
// when you're done reading all the files, do something...
console.log("before Callback", objToReturn);
callback(null, objToReturn);
}
);
}
// To call it:
stDirectory.readDirectory(env, function(err, files) {
if (err) {
res.sendStatus(500);
} else {
res.json(files);
console.log('Api files',files);
}
});
You should also consider using async.mapSeries() instead of async.eachSeries() and using a separate array (objToReturn).
Im trying to stub a pouchDB 'put' function but in an invoked function but it is failing.
my DB function-
var PouchDB = require('pouchDB')
var PendingDB = new PouchDB("")
module.exports.addPendingRequest = function(doc, callback){
PendingDB.put(doc, function(err, result){
if(err) {
console.log("Error in PendingDB: addPendingRequest");
console.log(err);
callback(err, null);
}
callback(null, result);
});
console.log("after put: inside addPendingRequest");
}
My Test Function:
var expect = require("chai").expect;
var PendingDB = require("../../lib/administration/PendingDB");
var PouchDB = require('pouchDB');
var sinon = require('sinon');
describe('Testing adding a request', function(){
it('should save the request with email', function(done){
var req = {
_id : "test#email.com",
first_name: "firstTest",
last_name: "test",
id: "test#email.com",
justif: "Testing Purposes",
}
var res = {};
var next = null;
console.log("after req, res, next");
var testOutput = {
success : "success"
};
console.log("after testOutput is set");
var PendingDBTest = sinon.stub(PouchDB.prototype, 'put', function(err, result){
console.log("in stub addReq");
});
console.log("after sinon.stub");
expect(function(){
PendingDB.addPendingRequest(req, function(err, response){
console.log("response");
console.log(response);
});
}).to.not.throw(Error);
expect(PendingDBTest.called).to.equal(true);
PendingDBTest.restore();
done();
})
})
Console:
after req, res, next
after testOutput is set
after sinon.stub
after put: inside addPendingRequest
Therefore PendingDB.put is never entered and my test PendingDBTest.called returns false, thus failing.
Stub on actual object, not on its prototype.
var PendingDBTest = sinon.stub(PouchDB, 'put', function(err, result){
...
Instead of stubbing you could write your tests with the in-memory adapters avaliable for PouchDB:
http://pouchdb.com/adapters.html
In NodeJS:
var PouchDB = require('pouchdb');
var testDB = new PouchDB('testDb', {
db: require('memdown')
});
Or in the Browser:
<script src="pouchdb.js"></script>
<script src="pouchdb.memory.js"></script>
<script>
// this pouch is ephemeral; it only exists in memory
var testDB = new PouchDB('testDB', {
adapter: 'memory'
});
</script>
For example of a project that tests in this way check out: https://github.com/hoodiehq/pouchdb-hoodie-api/tree/master/tests