Hello I am new to NodejS and still learning so I might have mistakes and I am trying to learn it by writing code and I am from java background. Asyc functions are still new to me.
Here is my question
I would like to assign user_id to each user from my code.
.post('/register', function (req, res, next) {
var username = req.body.uname;
var password = req.body.psw;
var email = req.body.uemail;
var fullname = req.body.fullname;
var user_id = sql_counts.sql_count()+1;
console.log('Your user id is'+user_id);
sql_connection.User.create({
username:username,
password:password,
email:email,
user_id:user_id
},function (err) {
if(!err){
console.log('Successful');
res.redirect('/registrationComplete');
}else{
console.log('Error creating');
}
});
});
And here is my sql_count function:
function sql_count() {
sql_connection.User.count().then(function (err) {
initCounter =err;
});
return initCounter;
};
I would like to understand more about calls backs since this is very new and confusing to me. Could anyone suggest some materials,links,videos... Although it seems to be understanding in the start I just dont understand it when I try using it. And also how to return values from callbacks to outter function?
Say
In the code given above how do I return value from the 'then' part to outer function sql_count() ?
Use MYSQL AUTO_INCREMENT feature to create a new user_id for each new user (i.e each new row) while inserting as follows
CREATE TABLE USERS( user_id INT NOT NULL AUTO_INCREMENT);
cheers
For Callbacks and Promises checkout this video and for latest await /async feature this video
You can use auto increment column in you mysql table it will automatically increase or generate id using random function. I will suggest you first one
Related
I'm creating my custom order id with auto-increment generator function for my project. I will state my question here, if you want to know the whole story please read below.
As written in the title, I need a way to reject my set to Firebase and it has to be done in 1 query. Currently, it will write my orderID to Firebase without rejecting it. But I need to reject if there is the same ID in the table.
The short version of my code will be posted here, the whole function will be posted below.
firebase.database().ref('orderCounter/orderIDsChecker/'+orderID).set({
id: orderID,
}, function(error) {
if (error) {
console.log('Order ID fail to generate. Regenerating new ID')
createOrderID(orderCounterRef);
} else {
console.log('Order ID created!')
}
});
}
The story,
I'm creating my own custom order id with auto-increment generator function for my project. The problem is that if multiple users creating order at the same time, it will generate the same id. Yes, I can use transaction() to solve the problem but I have no idea how to use it. Therefore, I have created my own version of the "transaction". With my method, I am able to prevent duplicates id unless 2 or more users create order within 1 second of gap. Or if anyone is kind enough to show me an example of how to write a transaction for my function, I thank you in advance.
The flow of the code is,
Get "currentMonth" and "orderIdCounter" from Firebase -> orderIdCounter +1 and update to Firebase -> start the process of generating order id -> Send the generated id to firebase -> If return success "order ID created", If not "got duplicate id" Re-run the whole process.
Below is the code for my order id generator function.
function createOrderID(orderCounterRef){
var childData = [];
var orderID;
//Get the Current Month and Order ID Counter from Firebase
orderCounterRef.on('value', function(snap) { childData = snapshotToArrayWithoutID(snap); });
var currentMonth = childData[0];
var orderIDCounter = childData[1];
if (orderIDCounter !== undefined){
//Update orderIDCounter on Firebase.
//This is to prevent duplicate orderID when multiple users is creating order at the same time.
var IDCounter = parseInt(orderIDCounter) + 1;
//Set IDCounter to 3 digits
IDCounter = ('00' + IDCounter.toString()).slice(-3);
firebase.database().ref('orderCounter/orderIDCounter').set(IDCounter);
//Handle the process to generate Order ID. Return in YYMMxxx(auto increment) format.
orderID = handleCreateOrderID(currentMonth, (parseInt(orderIDCounter) - 1));
//Check if duplicate ID on firebase
firebase.database().ref('orderCounter/orderIDsChecker/'+orderID).set({
id: orderID,
}, function(error) {
if (error) {
console.log('Order ID fail to generate. Regenerating new ID')
createOrderID(orderCounterRef);
} else {
console.log('Order ID created!')
}
});
}
return orderID;
}
My DB:
You should indeed use a transaction as you have mentioned in your question.
The following should do the trick:
//Declare a function that increment a counter in a transaction
function createOrderID() {
var orderIdRef = firebase.database().ref('orderId');
return orderIdRef.transaction(function(currentId) {
return currentId + 1;
});
}
//Call the asynchronous createOrderID() function
createOrderID().then(function(transactionResult) {
console.log(transactionResult.snapshot.val());
});
If you want to start the counter at a specific value, just create an orderId node in your database and assign a specific value to it, e.g; 1912000.
If you just want to start at 1, you don't need to create a node, it will be automatically created with the first call to the createOrderID() function.
Thank you, #samthecodingman & #Renaud Tarnec for your advice.
I took #samthecodingman's code and change a bit to fit my project. But I use generateOrderID() only to call the result and it works well. But you won't get any value with just the code. I call out another function (connectToFirebase) whenever users enter the page. I am not sure why it works or if this is the right way, but it works for me and that's good enough.
export function generateOrderID(){
var orderId;
var childData = [];
const orderCounterRef = firebase.database().ref('orderCounter/');
//Get the Current Month from Firebase
orderCounterRef.on('value', function(snap) { childData = snapshotToArrayWithoutID(snap); });
//Check ID format YYMMXXX (XXX=auto_increment). Hanlde auto_increment for Year and Month
handleOrderIdFormat(childData[0], orderCounterRef)
//transaction
orderCounterRef.child('orderId').transaction(function(currentId) {
orderId = (currentId||0) +1;
return orderId;
}, function(err) {
if( err ) {
console.log(err)
}
});
return orderId;
}
export function connectToFirebase(){
//Connection Firebase Database
const orderCounterRef = firebase.database().ref('orderCounter/');
orderCounterRef.on('value', function(snap) { });
}
I have a driver.js that contains a driver schema. Also the driverController.js, which contains my rest methods. GET, POST, DELETE, and PUT.
What i would like to do is
GET - http://localhost:3000/drivers?available=true
and have it return all of the drivers that are available.
My driver schema simply looks like this:
var mongoose = require('mongoose');
var DriverSchema = new mongoose.Schema({
name: String,
available: Boolean,
latitude: Number,
longitude: Number
});
mongoose.model('Driver', DriverSchema);
module.exports = mongoose.model('Driver');
I looked at some documentation, but I haven't been able to do anything.
Here's my GET method in which I'm attempting to add parameters
// GETS ALL DRIVERS FROM THE DATABASE
router.get('/', function (req, res) {
Driver.find({}, function (err, driver) {
if (err) return res.status(500).send("There was a problem finding the drivers.");
var available = req.query.available;
if (available == driver.available )
res.status(200).send(available );
else
res.status(200).send("Nice! " + driver.available);
});
});
This comparison doesn't ever work. It always goes to the else statement. I'm not quite sure why but the output is "Nice! undefined" Even though I have plenty of drivers in my database, and if I only put inside the else statement
res.status(200).send("Nice! " + driver);
Then it gives me the list of drivers.
Nonetheless, I would like to be able to use query parameters in order to find drivers.
Any hints or tips would be greatly appreciated, as this is a project and I have never worked with restAPI, or javascript before. Thanks!
NOTE: Mongoose, express. node.js, and mongoDB are being used.
if I only put inside the else statement res.status(200).send("Nice! " + driver); Then it gives me the list of drivers.
it's a list of drivers, with if (available == driver.available ) you're comparing a boolean with an array of objects,
instead of fetching all the drivers and checking if they have availabe == true , add the condition to the .find() and return the result :
// GETS ALL DRIVERS FROM THE DATABASE
router.get('/', function (req, res) {
Driver.find({ available : req.query.available }, function (err, drivers) {
if (err) return res.status(500).send("There was a problem finding the drivers.");
res.status(200).send(drivers);
});
});
EDIT :
you can do this to add filter depending on the query string :
// GETS ALL DRIVERS FROM THE DATABASE
router.get('/', function (req, res) {
var params = {};
Object.keys(req.query).forEach((v, k) => params[k] = v);
Driver.find(params, function (err, drivers) {
if (err) return res.status(500).send("There was a problem finding the drivers.");
res.status(200).send(drivers);
});
});
having ?name=Wario&available=true will create an object like { name : 'wario', available : true and pass it to the .find()
I've got CouchDB setup with Couchperuser. Locally I use PouchDB.
I'm building a mobile application with Cordova. It's about a todo list. with login, so users have there own list.
When I create a new user it automatically makes a new database for this user.
now, when that user is logged in and adds new todo's to his list, they go in the main database because I use :
var db = new PouchDB('http://localhost:5984/main', {skipSetup: true});
What I want to achieve is that the todo created by the specific user goes into his database. for example:
var db = new PouchDB('http://localhost:5984/userdb-41646d696e32', {skipSetup: true});
How can I automatically do this? so the var db = the users database?
I've looked around the internet but could not find anything about this.
Hope someone can help me with this scenario.
EDIT:
I'll add the code that I use for adding the todo:
var db = new PouchDB('http://localhost:5984/main', {skipSetup: true});
function addToDoItem() {
//get info
var toDoTitle = document.getElementById('toDoTitle').value;
var toDoDescr = document.getElementById('toDoDesc').value;
var addItem = {
_id: new Date().toISOString(),
title: ToDotitle,
description: ToDoDescr
};
db.put(addItem ).then(function (result){
console.log("Added to the database");
console.log(result);
}).catch(function (err){
console.log("someting bad happened");
console.log(err);
});
}
Find out, this is the way to fix it. thought of it already but seemed a bit of a cheap solution. anyway, this is the only code example I found on the internet.
dbs.remote.private = pouchDB(DATABASE.URL + "userdb-" + _convertToHex(username), {
auth: {
username: username,
password: password
}
});
i have a simple question and i have read a lot of same issues here, but these are not exact the same or doesn't work for me :-(
I have a REST function called "addevent". The function gets a json input (req) and iterate through the json array to get some IDs to store them in an extra Array. That works perfect!
After that, the function should search in a mongodb for every single id and store some extra informations from this ID (e.g. the stored URL of this ID). With "console.log(result.link)" it works again perfect. But my problem is that, that i need to store this link in an extra Array (urlArray).
So how can i save the result of collection.findone(). I read something about, that findone() doesn't return a document, but a cursor? what does that mean? How do i have to handle that in my case?
That's the code:
exports.addevent = function(req, res) {
var ids = req.body;
var pArray = new Array();
var urlArray = new Array();
var eventName = ids.name;
for(var i in ids.photos) {
photoArray.push(ids.photos[i]);
var id = ids.photos[i]._id;
var collection = db.get().collection('photos');
collection.findOne({'_id':new mongo.ObjectID(id)},function(err, result) {
console.log(result.link);
}
)
}
Many thanks!
-------------------- Update --------------------
Ok, i think that has something to do with the asynch Callbacks. I found an article, but i don't know how to implement it in my case.
http://tobyho.com/2011/11/02/callbacks-in-loops/
And something about "promises" in javascript.
You can save the result of your search doing something like:
var foundPhoto = collection.find({_id':new mongo.ObjectID(id)}, function(err, photo){
if(!err){
return photo;
} else {
console.log(err)
return null;
}
});
This way you get the return statement of your query in the "photo" variable.
I am making a new webservice where i send a curl command with JSON and the JSON contains a array as
[{tempid:1,email:abc#123,address:asd},{tempid:2,email:abc#12345,address:asd45},{tempid:3,email:abc#1234,address:asd4}]
Now when i pass and insert the array in a mysql table tempid is just to show a mapping to the user to the contact id generated in the database as tempid:1 is now inserted and in database it has cid 120 , like this for tempid2 and 3 ,
But when i am trying to show the client the updated values it shows only one value , last last change not the whole updated Array. Its becuase of the async nature of the connection.querry function , so i need help in this , here is my webservice
contactadd webservice -->
for(var i=0;i<=request.body.contact.length-1;i++)
{
if(request.body.contact[i].tempid)
{ var ardata=new Array();
var o=request.body.contact[i];
pair=Object.keys(o).map(function(a){ return [a, o[a]] });
AM.addcontact(pair,request.session.user,request.body.contact.length,function(e,o){
if(!o)
{
response.send('something went wrong'+e);
}
else
{
//response.send(o);
}
});
}
}
Here is the update function in the database.js script -->
//ContactSync-addcontact module for database
exports.addcontact=function (arr,email,addnum,callback)
{
var counter=0;
var uid;
var data=new Array();
var showinsert=new Array();
var values=new Array();
var datatable=new Array();
var inserting=new Array();
var tempid=0;
connection.query('SELECT UID FROM user where email1="'+email.email+'"',function(err,rows,fields){
if(err)
{
throw err;
}
else
{
if(rows[0]!=undefined)
{
uid=rows[0]['UID'];
}
else
{
uid="no id in database";
}
}
});// get the UID of the inserting user
// make array of user provided data
for(var j=0;j<=arr.length-1;j++)
{
if(arr[j][0]!='tempid')
{
data.push(arr[j][0]);
}
else
{
tempid=arr[j][1];
}
}
connection.query('SELECT column_name FROM information_schema.columns where table_schema="webservice" AND table_name="usercontacts"',function(err,rows,fields){
if(err)
{
throw err;
}
else
{
for(var i=0;i<=rows.length-1;i++)
{
datatable.push(rows[i]['column_name']);
}
}
for(var k=0;k<=datatable.length-1;k++)
{
if(inArray(data[k],datatable))
{
inserting.push(data[k]);
}
}
if(inserting.length>0)
{
for(var z=0;z<=arr.length-1;z++)
{
if(inArray(arr[z][0],inserting))
{
values.push('"'+arr[z][1]+'"');
}
}
// Insert tempid values and data in the usercontacts table with inserting and values
connection.query('INSERT INTO usercontacts (cid,uid,'+inserting+') VALUES("","'+uid+'",'+values+')',function(err,rows,fields){
if(err)
{
throw err;
}
else
{
connection.query('SELECT * FROM usercontacts WHERE uid="'+uid+'" ORDER BY cid DESC LIMIT 0,'+addnum+'',function(err,rows,fields){
if(err)
{
throw err;
}
else
{ showinsert.push('temp-id: '+tempid+',cid:'+rows[0].cid+',uid:'+uid);
//for(var i=0;i<=inserting.length-1;i++)
forEach(inserting,function(row,index)
{
showinsert.push(inserting[index]+":"+values[index]);
counter+=1;
});
callback(null,showinsert);
}
});
}
});
//insertion finished
}
else
{
callback("Please Provide atleast one field to enter with tempid");
}
});
}
I just need to insert all the callback in a array which has been inserted and show user that array ,please help , completely stuck and then only i am trying StackOverflow.
Thank you for reading till the end BTW
I'm not sure what the specific problem is, but there are some problems with the code you've shared that will bite you sooner or later. One of these may be causing your problem.
Race conditions
If the query SELECT UID FROM user where email1= for any reason takes longer than the SELECT column_name FROM information_schema.columns just below it then you won't have a value for the variable uuid and your logic will fail. Remember that these calls are non-blocking, so you can't rely on one finishing before the other one unless they're nested or use another flow-control mechanism (As #Tracker points out, async is popular).
Catching edge cases
In the line below you're assigning a string value to the uid variable and then continuing to use that variable even though it now contains an error message.
uid="no id in database";
Doing that means that your code later on will have trouble reacting. Instead use a different variable, leave the uid = undefined or immediately return the callback with an error, e.g.
return callback(new Error("user not found"));
Reporting errors
Don't throw errors in Node unless you want to kill the process, e.g. dependency problems during server startup. It doesn't work like Java, async errors are not caught by try/catch and will kill your process or leave you in a state that's hard to reason about. Instead make the error object your first parameter to the callback and return it immediately, like this:
if ( err ) return callback(err);
Then in your client code you can always check the first parameter to see if there was a problem.
Security problem
As #Tracker mentioned, don't ever do the this:
connection.query('SELECT UID FROM user where email1="'+email.email+'"', ...
If the value of the variable is passed through as "; drop table user; or similar then you're in trouble. Instead you can use node-mysql's build in escaping like this:
connection.query('SELECT UID FROM user where email1=?', [email.email], ...
Whitelist
You're querying information_schema.columns in order to detect which fields are valid then inserting them into usercontacts. This is a clever trick, but increases a 3 query process to 4 queries, and raises questions if there are any fields that a user shouldn't be inserting data into. Using a column whitelist may seem like more code to maintain, but would actually be simpler than all the code required to match columns dynamically.
Arrays
I don't see the source for the function inArray() but it looks like it does the same as Array.prototype.indexOf() so it may be better to use that. e.g.
if ( datatable.indexOf(data[k]) > -1 ) inserting.push(data[k]);
Every line of custom code you can delete is a line of code you don't have to maintain.