Is any possible to increment var licznik in this block of code?
I try sth like this, But always receives 0. Could someone explain me what I'm doing wrong?
rows.forEach(function(record) {
var licznik = 0;
var offer = manager.createOffer('76561198252553560');
inventory.forEach(function(item) {
if(licznik <= record.amount) {
if(item.market_hash_name == record.real_name) {
var asid = item.assetid;
(function(licznik){
connection.query('SELECT count(id) as wynik FROM used where asset_id = \'' + asid + '\'', function(err, wiersze) {
if (wiersze[0].wynik == 0) {
var employee = {
asset_id: asid,
trans_id: record.tid
};
connection.query('INSERT INTO used SET ?', employee, function(err, res) {
if (err) throw err;
offer.addMyItem(item);
console.log(licznik);
&licznik++;
});
}
});
})(licznik);
}
}
});
});
As the comment on your original question points out, I have no context for what this code is actually trying to accomplish. What I can tell you is that your callbacks supplied to connection.query are NOT fired on each iteration of the forEach. The whole reason connection.query takes a callback is because you don't know when the operation will complete. Node is designed to be asynchronous so all it does on each iteration of the forEach loop is begin the query. The callback supplied to the query could be invoked at any time which also means that a query that fired after another query could potentially fire its callback before the callback from the first query. It just depends on how long each query takes.
If you need licznik to be incremented on every iteration of the forEach then you need to increment it after your if statement.
rows.forEach(function(record) {
var licznik = 0;
var offer = manager.createOffer('76561198252553560');
inventory.forEach(function(item) {
if(licznik <= record.amount) {
// .... omitted for brevity
}
licznik++; // <-- increment here, outside of the closure.
});
});
Again, I have zero clue what you're actually trying to do with that variable so this may not solve your real problem, but that's the way to get it to increment in that loop.
PS - You may not be understanding that you actually have two licznik variables here. You create a new one when you wrap all your logic in a closure function like you did. If you change the variable declared at the top of your closure function you'll see that it's not the same variable as the one outside the closure function.
rows.forEach(function(record) {
var licznik = 0;
var offer = manager.createOffer('76561198252553560');
inventory.forEach(function(item) {
if(licznik <= record.amount) {
if(item.market_hash_name == record.real_name) {
var asid = item.assetid;
(function(licznik2) { // <-- notice this is a new variable
connection.query('SELECT count(id) as wynik FROM used where asset_id = \'' + asid + '\'', function(err, wiersze) {
if (wiersze[0].wynik == 0) {
var employee = {
asset_id: asid,
trans_id: record.tid
};
connection.query('INSERT INTO used SET ?', employee, function(err, res) {
if (err) throw err;
offer.addMyItem(item);
console.log(licznik2);
licznik2++;
});
}
});
})(licznik);
}
}
});
});
Related
I am calling function in order to insert some values into a database table using mysql module of node.js. The function is called inside a for loop and I can get the last insertId of each INSERT query inside the function.
MY PURPOSE
I want to store these id's to an array in to order to use them later in my code but I cannot do that.
- FUNCTION CALL
for(var i=0;i<some_number;i++){
if (<something is true>){
var lastid = [];
//Function calling
function_a(x, y, z, w, function(error, result) {
if(!error){
lastid.push(result.insertId);
}
//To Do
else{}
});
}
}
- FUNCTION
function function_a(a, b, c, d, callback){
//Connection to the DB
const con = mysql.createConnection({
host: 'host',
user: 'user',
password: 'password',
database: 'database'
});
//DB query
var query = "INSERT INTO my_table (column1, column1, column1, column1) VALUES ('"+a+"', '"+b+"', '"+c+"', '"+d+"')";
con.query(query, (err, rows) => {
var e = rows.insertId;
return callback(err, e);
});
con.end();
}
The problem is that I cannot use the id's outside the function.
Any idea how can I do that?Is this about variable scope?
Several problems here, and yes, they are partly about variable scope.
Put var lastid = []; before the for loop, so you can use it after the loop. However, as you have callback mechanism inside the loop, you must wait for the whole loop to finish (all callbacks called from 0 to some_number-1, in order to have the right values in lastid array. It's a messy thing with callbacks, but you can do it with them or with promises. You can Google for callback handling in for loops.
The function function_a is a asynchronous function. In your case you can use async module to do this task:
var taskIds = Array.apply(null, {length: some_number}).map(Number.call, Number);
var lastid = [];
async.eachLimit(taskIds, 32, function (taskId, done) {
if (<something is true>) {
function_a(x, y, z, w, function(error, result) {
if(!error){
lastid.push(result.insertId);
}
//To Do
else{}
done()
});
} else {
done()
}
}, function () {
// Do some thing with lastid
console.log(lastid);
});
I am writing a small Node js application for automatic vehicle location system.
Here is the code for where I am getting trouble.
markerData contains 4 rows but only in the log I can see the last row.
for (var i = 0, len = markerData.length; i < len; i++) {
var thisMarker = markerData[i];
sql.connect(config, function (err) {
var request = new sql.Request();
request.input('myval', sql.Int, thisMarker.id);
request.query('SELECT d.id, d.name, d.lastupdate, p.latitude, p.longitude, p.speed, p.course FROM dbo.devices AS d INNER JOIN dbo.positions AS p ON d.positionid = p.id AND d.id = p.deviceid WHERE (d.id = #myval)', function (err, recordset2) {
if (typeof recordset2 != 'undefined') {
thisMarker.position.lat = recordset2[0].latitude;
thisMarker.position.long = recordset2[0].longitude;
console.log(recordset2[0].id);
}
});
});
}
Please help me to solve the issue.
As var is not a block level variable in terms of scope, when `sql' module takes time to connect to the database asynchronously, the synchronous loop may change the value of the variable that's why you have the last row printed since the variable holds the reference to the last object at the time of successful connection.
Instead of _.each, I would recommend to use async module with async.each since you have few asynchronous operation to get rid of a synchronous loop.
You can check for samples here,
http://justinklemm.com/node-js-async-tutorial/
Here is your updated code with async.each
-> Install async module with npm install async --save
-> Then add the below reference in the required place,
// Reference
var async = require('async');
-> Modified code:
sql.connect(config, function (err) {
if(err) {
console.log('Connection error: ');
console.log(err);
} else {
async.each(markerData, function(thisMarker, callback) {
var request = new sql.Request();
request.input('myval', sql.Int, thisMarker.id);
request.query('SELECT d.id, d.name, d.lastupdate, p.latitude, p.longitude, p.speed, p.course FROM dbo.devices AS d INNER JOIN dbo.positions AS p ON d.positionid = p.id AND d.id = p.deviceid WHERE (d.id = #myval)', function (err, recordset2) {
if(err) {
console.log(err);
callback();
} else {
if (typeof recordset2 != 'undefined') {
thisMarker.position.lat = recordset2[0].latitude;
thisMarker.position.long = recordset2[0].longitude;
console.log(recordset2[0].id);
} else {
console.log('Recordset empty for id: ' + thisMarker.id);
}
callback();
}
});
}, function(err){
if(err) {
console.log(err);
}
});
}
});
I'm not entirely sure how your library works, but presumably recordset2 is an array of records. recordset2[0] is therefore the first record. If you want the next one you should probably try recordset2[1] and so on and so forth.
Arrays: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array
You'll probably need to loop through all the elements in the array at some point. use a for loop for that:
for (var i = 0; i < recordset2.length; i++ {
console.log(recordset2[i])
}
That will print out everything your query returns.
I posted a question before and realized my problem actually was async functions. I managed to work out most of it, but I got one little problem left. Using async I used waterfall to create an order for the some queries...
exports.getMenu = function(id_restaurant, callback){
async.waterfall([
async.apply(firstQuery, id_restaurant),
secondQuery,
thirdQuery,
fourthQuery,
formMenu
], function(err, result){
if(err){
console.log(err);
}
callback(result);
});
};
Everything works until fourthQuery, where I have to loop to get all dishes of a menu.
function fourthQuery(array_totalP, array_nombresSecc, array_secciones, callback){
var size = array_nombresSecc.length;
var array_secciones = array_secciones;
var array_nombresSecc = array_nombresSecc;
var dishes = [];
pool.getConnection(function(err, connection) {
if(err) {
console.log(err);
callback(true);
return;
}
for (var i = 0; i < size; i++) {
connection.query("SELECT name, price FROM menu_product WHERE id_seccion = ? AND active = 1", [array_secciones[i]],
function(err, results2) {
if(err) {
console.log(err);
callback(true);
return;
}
console.log("Result query 4 " + JSON.stringify(results2));
dishes[i] = results2;
console.log("VALOR PLATILLOS EN i : " + JSON.stringify(dishes[i]));
// this prints the result but only if it has a value over 2
});
};
}); // pool
console.log("I'm sending " + dishes); // this logs an empty array
callback(null, dishes, array_nombresSecc);
};
So what i can see that happens from printing the value of 'i' each loop is that it always has the value of 2. Because that's 'size' value. Also, even though it's saving results of index '2' I believe the callback is being done even before the for loop is done, because my fifth function is recieving an empty array.
How can i make my code wait to callback until my for loop is done?
NOTE: Sorry, part of my code is in spanish, tried to translate the important parts of it.
There are a few ways to handle this, one is to look into promise architecture. Promise.all will let you supply one callback to handle the values from each child promise.
To use what you've already got, however, I'd push the values into your dishes array, rather than assigning them specifically to i indexes, then check the size of that array at the end of each connection. When the array length matches the size, fire the callback. (as seen below)
If you need a way to tie each result to that specific i value, I'd recommend pushing them as an object
dishes.push({'index': i, 'dish': results2})
Afterward, if you need the array of just dishes, you can sort the array by that index value and run a map function.
dishes.sort(function(a,b){ return a.index - b.index; })
dishes = dishes.map(function(a){ return a.dish })
Here's the code adjusted:
function fourthQuery(array_totalP, array_nombresSecc, array_secciones, callback) {
var size = array_nombresSecc.length;
var array_secciones = array_secciones;
var array_nombresSecc = array_nombresSecc;
var dishes = [];
pool.getConnection(function(err, connection) {
if (err) {
console.log(err);
callback(true);
return;
}
for (var i = 0; i < size; i++) {
connection.query("SELECT name, price FROM menu_product WHERE id_seccion = ? AND active = 1", [array_secciones[i]],
function(err, results2) {
if (err) {
console.log(err);
callback(true);
return;
}
console.log("Result query 4 " + JSON.stringify(results2));
dishes.push(results2)
if(dishes.length == size){
console.log("I'm sending " + dishes);
callback(null, dishes, array_nombresSecc)
}
console.log("VALOR PLATILLOS EN i : " + JSON.stringify(dishes[i]));
// this prints the result but only if it has a value over 2
});
};
}); // pool
;
};
Since you're already using the async, I would suggest replacing the for() loop in fourthQuery with async.each().
The updated fourthQuery would look like this:
function fourthQuery(array_totalP, array_nombresSecc, array_secciones, callback){
var size = array_nombresSecc.length;
var array_secciones = array_secciones;
var array_nombresSecc = array_nombresSecc;
var dishes = [];
pool.getConnection(function(err, connection) {
if(err) {
console.log(err);
callback(true);
return;
}
async.each(array_secciones,
function(item, itemCallback) {
// Function fun for each item in array_secciones
connection.query("SELECT name, price FROM menu_product WHERE id_seccion = ? AND active = 1", [item],
function(err, results2) {
if(err) {
console.log(err);
return itemCallback(true);
}
console.log("Result query 4 " + JSON.stringify(results2));
dishes.push(results2);
console.log("VALOR PLATILLOS EN i : " + JSON.stringify(dishes[dishes.length-1]));
// this prints the result but only if it has a value over 2
return itemCallback();
});
},
function(err) {
// Function run after all items in array are processed or an error occurs
console.log("I'm sending " + dishes); // this logs an empty array
callback(null, dishes, array_nombresSecc);
});
}); // pool
};
Alternatively, you can use async.map(), which handles gathering the results in the final callback so doesn't rely on the dishes variable.
i am quiet new to java script and node js.
i have a problem with a simple function that i call, and it gets done more than one time.
this is my code
app.post('/checkGetSensorIds', function (req, res) {
var tables=['temperature', 'pressure', 'linear_acceleration'];
var ids= [1];
DButils.checkAllSensorsForId(connection, 1 , tables , function(idHasSensorsInfo){
console.log("idHasSensorsInfo is: \n" , idHasSensorsInfo);
});
res.end();
});
/*this function gets a user Id, and the table of all sensors the customer wants, and return true if this
user id has information in all the sesnsor tables that were requested, otherwise returns false*/
exports.checkAllSensorsForId= function(dbConnection, id , sensorsTables, callback){
var sensorsTablesLength= sensorsTables.length;
for (var i = 0; i < sensorsTables.length; i++) {
var tableName= sensorsTables[i];
DButils.checkSingleSensorForId(dbConnection, id, tableName, function(idHasSensorInfo){
if(idHasSensorInfo == false){
callback(false);
return;
}
//in case user have all info in db, we get here and need to return false
if(i == sensorsTablesLength){
callback(true);
return;
}
});
}
};
/*this function gets a user Id, and a single sensor table, and returns true if the user has information
in the requested sensor table, otherwise returns false*/
exports.checkSingleSensorForId= function(dbConnection , id , sensorTable, callback){
var myQuery = 'SELECT count(*) as IdCount FROM ' + sensorTable + ' WHERE id= ' + id;
var query = dbConnection.query(myQuery, function (err, row, result) {
console.log(query.sql);
if (err) {
console.log("checkSingleSensorForId error");
console.error(err);
return;
}
var count= row[0].IdCount;
var idHasSensorInfo = (count > 0);
callback(idHasSensorInfo);
});
};
console.log("idHasSensorsInfo is: \n" , idHasSensorsInfo); is a line that invoked 3 times, while should be only once.
someone has any idea why, and what i need to do to fix it?
You have this line:
DButils.checkAllSensorsForId(connection, 1 , tables , function(idHasSensorsInfo){
console.log("idHasSensorsInfo is: \n" , idHasSensorsInfo);
});
Then you have this:
exports.checkAllSensorsForId= function(dbConnection, id , sensorsTables, callback){
...
for (var i = 0; i < sensorsTables.length; i++) {
...
callback();
...
}
};
So the callback line will be invoked as many times as you call it, which in your case is probably 3 - all it does is call the function from above, so thats why you see it invoked 3 times.
I'm not sure exactly what you are trying to do, but if the callback should be only called once, make sure its ran only once - if it should 'cancel' the for - add a condition to the for or use a promise to resolve whenever you are ready.
First off I thought I'd get this problem solved after this great thread: nodeJs callbacks simple example
However, I am still unsure of how to proceed. Like the title hints at: I need a callback given to a callback who already has node arguments being passed to it
Code:
(function()
var reqs = {
http: require('http'),
path: require('path'),
fs: require('fs')
};
reqs.http.createServer(function (request, response) {
response.writeHead(200, {
'Content-Type': 'text/plain'
});
response.end('Hello HTTP!');
}).listen(8080);
var printCount = function(count) {
console.log(count);
};
var callCount = function(err, list, callback) {
var count = 0;
if(err) throw err;
// console.log(err);
for (var i = 0; i < list.length; i++) {
// console.log(reqs.path.extname(list[i]));
if(reqs.path.extname(list[i]) === ".png" || reqs.path.extname(list[i]) === ".jpg")
{
count++;
console.log(count);
}
}
callback(count);
};
//count images from executing directory
var countImages = function(dirName) {
var imageCount = reqs.fs.readdir(dirName, callCount(null, null, printCount));
};
countImages(__dirname);
})();
I think the key line here is
var imageCount = reqs.fs.readdir(dirName, callCount(null, null, printCount));
I'm passing the printCount function to the same function that is called back after fs.readdir asynchronously executes but it seems that me passing null to its first two arguments is overriding Node functionality that passes the callback err and list automatically. How can I get around this? I simply want to count the images in the executing directory and be able to store that value in my main function.
Pretty new to event style programming. Any extra reading suggestions are welcome. There is tons of content out there but I really want to get this up and running for a meeting this weekend. Thanks guys!
you can't quite do what you are doing, you are doing callCount(null, null, printCount) which executes the function. But you need to pass a function as a callback. What you want is something like the following, which captures the call back you want and returns a function you can pass as a callback to your api call
var callCount = function(callback) {
return function(err, list) {
var count = 0;
if(err) throw err;
// console.log(err);
for (var i = 0; i < list.length; i++) {
// console.log(reqs.path.extname(list[i]));
if(reqs.path.extname(list[i]) === ".png" || reqs.path.extname(list[i]) === ".jpg")
{
count++;
console.log(count);
}
}
callback(count);
}
}
and then
reqs.fs.readdir(dirName, callCount(printCount));