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my functions are mixed and the engine executing what ever he wants

so i was told to Present a loader to the user when a call is made to the server (indicating the server is calculating) Present an error to the user if the input number is more than 50, and do not send a server request Try passing the number 42 to the server. The server will send back an error, present this error to the user.
now what i did is everything besides the last error to present it to the user.
i have tried everything i could think of, and no matter what the user types, it displays both of the messages.
this is my code:
const clcBtn = document.getElementById("calcButton");
let clcInput = document.getElementById("calcInput");
const result = document.getElementById('paragraph');
const loader = document.getElementById('spinner');
const error = document.getElementById('error-message');
const serverError = document.getElementById('server-error');
clcBtn.addEventListener("click", calcFunc);
function numValidate(value) {
if(value > 50) {
return false;
}
return true;
}
function calcFunc() {
if (!numValidate (clcInput.value)) {
error.style.display = "block"
setTimeout(() => {
error.style.display = "none";
}, 5000);
console.error("Can't be larger than 50") // only bec it's a cool feature :D
return;
}
loader.classList.add("spinner-border");
fetch(`http://localhost:5050/fibonacci/${clcInput.value}`).then(function (response) {
return response.json().then(function (data) {
result.innerHTML = data.result;
});
});
setTimeout(() => {
loader.classList.remove("spinner-border");
}, 1000);
}
this is my code with what i have tried to add (on of the things i have tried.. this is the best output i could come with)
code:
// additional code to present to the user the error message if the input value is equal to 42.
clcBtn.addEventListener("click", errMsg);
function numValidateTwo(value) {
if(value === 42) {
return true;
}
return false;
}
function errMsg() {
if (!numValidateTwo (clcInput.value)) {
serverError.style.display = "block";
}
return;
}
a little bit more about what i am trying to achieve:
i want to present this error message to the user, whenever the input value is equal to 42.
is it related to async or callback? which i need to go through the lectures again.. but right now i need to solve this bec i have no time.
what did i do wrong ?
and how i can make it work?
can someone explain this to me?
thanks in advance!

Get and check a value from JSON read in NodeJS

I'm trying to check if a user exists (registered on a json file).
Unfortunately I don't find a valid solution in all Stack Overflow that gives me a simple "true" in a callback.
The version closest to a solution
Experiment V1 :
let userExist;
function check(){
console.log("CHECK!");
return userExist = true;
}
// check(); if this, return true... obvious.
//// check if user exist
server.readFileSync(filepath, 'utf8', (err, data) =>
{
let json = JSON.parse(data),
userlist = json.allusers;
for (let key in userlist)
{
if ( userlist[key].email == req.body.user_email )
{
console.log("FINDED EQUAL");
check(); // return undefined ???
}
}
});
console.log("userExist value : "+userExist);
differently formulated the debugs also appear, but "true" never returns.
note: yes, JSON is read correctly. If everything works inside the readfile, you immediately notice the same emails.
output: "undefined"
Log: total bypassed
Experiment V2 :
In this case (with asynchronous reading) it returns all the debugging (but the "true" remains undefined)
The problem with the asynchronous is that I have to wait for it to check to continue with the other functions.
//// check if user exist
server.readFile(filepath, 'utf8', (err, data) =>
{
let json = JSON.parse(data),
userlist = json.allusers;
for (let key in userlist)
{
if (/* json.allusers.hasOwnProperty(key) &&*/ userlist[key].email == req.body.user_email )
{
console.log("FINDED EQUAL");
check();
}
}
});
var userExist;
function check(userExist){
console.log("CHECK!");
return userExist=true;
}
console.log("userExist value : "+userExist+"");
server listening on: 8080
userExist value : undefined
CHECK!
FINDED EQUAL
Experiment V3 :
after the various suggestions I come to a compromise by using the syntax for the async functions.
This allowed to reach an ordered code, but despite this it is not possible to wait for the results and export them out of the same function (this is because node itself is asynchronous! Therefore it has already gone on!)
using a "message" variable to check if it could return an object I did so:
//simple output tester
var message;
// create a promise
let loopusers = new Promise( (resolve)=>{
server.readFile( filepath, 'utf8',
(err, data) => {
let json = JSON.parse(data),
userlist = json.allusers,
findedequal;
console.log("CHECK USERS IN DB...for "+userlist.length+" elements");
// loop all items
for (let key in userlist)
{
console.log("Analyzed key ::: "+key);
if ( userlist[key].email == req.body.user_email )
{
console.log("CHECK : user isn't free");
findedequal=true;
resolve(true); // return the result of promise
}
else if(key >= userlist.length-1 && !findedequal )
{
console.log("CHECK : User is free ;)");
resolve(false); // return the result of promise
}
}
// call the action
createuser();
});
});
// when promise finished --> start action
async function createuser(message)
{
let userExist = await loopusers;
console.log("userExist: "+userExist);
if(userExist)
{
message = { Server: "This user already exists, Try new e-mail..."};
}
else
{
message = { Server: "Registration user -> completed..."};
}
// return values
return message;
};
It is also possible to use the classic syntax via "then". For exemple:
//simple output tester
var message;
// create a promise
let loopusers = new Promise( (resolve)=>{
...
});
loopusers.then( (response)=>{
...
})
Then I realized that it was easy to simplify even more by calling the functions directly from the initial one:
var message;
// create a promise --> check json items
server.readFile( filepath, 'utf8',
(err, data) => {
let json = JSON.parse(data),
userlist = json.allusers,
findedequal;
console.log("CHECK USERS IN DB...for "+userlist.length+" elements");
for (let key in userlist)
{
console.log("Analyzed key ::: "+key);
if ( userlist[key].email == req.body.user_email )
{
console.log("CHECK : user isn't free");
findedequal=true;
createuser(true); // call direct function whit params true
}
else if(key >= userlist.length-1 && !findedequal )
{
console.log("CHECK : User is free ;)");
createuser(false); // call direct function whit params false
}
}
});
// start action
function createuser(userExist)
{
if(userExist)
{
message = { Server: "This user already exists, Try new e-mail..."};
}
else
{
message = { Server: "Registration user -> completed!"};
}
// return values
return message;
};
debugging is taken and written
the message is lost outside the aSync function
Experiment V4 Final! :
Finally, after many attempts the solution! (Yes... But know it's not Async)
If we allocate in a variable the reading becomes synchronous the whole model and we return to the simple one
let message,
file = server.readFileSync(filepath, 'utf8'), // read sync
json = JSON.parse(file), // now parse file
userlist = json.allusers, // get your target container object
userExist,
findedequal;
console.log("CHECK USERS IN DB...for "+userlist.length+" elements");
for (let key in userlist)
{
console.log("Analyzed key ::: "+key);
if ( userlist[key].email == req.body.user_email )
{
console.log("CHECK : finded equal value on key ["+key+"] - user isn't free");
findedequal=true;
userExist = true;
}
else if(key >= userlist.length-1 && !findedequal )
{
console.log("CHECK : User is free ;)");
userExist = false;
}
}
if(userExist)
{
console.log("└ EXIT TO CHECK --> Can't create user, function stop.");
message = { Server: "This user already exists, Try new e-mail..."};
}
else
{
console.log("└ Exit to check --> New user registration ...");
message = { Server: "Registration user -> completed!"};
}
}
return message;
Now:
It's all sync and all log is perfect
all var is checked
all return... return
** Final conclusions: **
Is it possible to retrieve an ASync variable in node?
As far as I understand so far ... no.
Node is async by its nature, therefore recovering information that is not saved and then recovered from a DB is left behind among the things to do, becoming unrecoverable if you use it as in this post.
However ... if the purpose is to make reading a file synchronous, the answer was simpler than expected.
A special thanks to: Barmar; Austin Leehealey; C.Gochev;

The problem is that you are calling console.log("userExist value : "+userExist+"");
too early. At the moment that you call that line, userExist is not defined yet. This is because the server.readFile() function requires a callback and that callback function is executed once it has read the file. However, reading files often take time and so the program keeps going. It executes console.log("userExist value : "+userExist+""); and then goes back to the callback function and defines userExist as true.
If you want more information on what callbacks are look at the link below. Callbacks are a defining feature of Nodejs and understanding them is essential to any Node website.
https://medium.com/better-programming/callbacks-in-node-js-how-why-when-ac293f0403ca
Try something like this.
let userExist;
function check(){
console.log("CHECK!");
return userExist = true;
}
// check(); if this, return true... obvious.
//// check if user exist
server.readFileSync(filepath, 'utf8', (err, data) =>
{
let json = JSON.parse(data),
userlist = json.allusers;
for (let key in userlist)
{
if ( userlist[key].email == req.body.user_email )
{
console.log("FINDED EQUAL");
check(); // return undefined ???
console.log("userExist value : "+userExist);
}
}
});

Firebase value is undefined when it is not supposed to be

I am working on a firebase project. During testing the
return user.val().name;
will return an
undefined
value however the
console.log(user.val().name)
will return the actual string stored in the .name field. Why is that. Also even if assign the
user.val().name
to a variable, the variable remains undefined.Please help figure out why this happens. I am printing it to a csv.
Here is my code:
var database = firebase.database();
var ref2 = database.ref('information/');
var id;
var name;
ref2.on("value", function (one) {
one.forEach(function (two) {
if (typeof two.val().Id !== 'undefined') {
id = two.val().Id;
name = program(id); //name undefined
}
else {
id = "";
}
csv = name + "," + id +"\n";
});
download(csv);
});
};
function program (id) {
var database = firebase.database();
var ref = database.ref("users/" + id + "/");
ref.on('value',function(user){
if (typeof user.val().name === 'undefined') {
return null;
}
else {
console.log(user.val().name); //this doesnt show undefined
return user.val().name; //this shows undefined when appended to a html element
}
})
}
Note: In the firebase database, the name value is not null. It has a string added to it.

I second with Frank's reason on why your function program() doesn't work. Because ref.on('value'... makes an asynchronous call, program() does not wait for the completion of ref.on and exists with an undefined return value.
What you could instead do is use Promises. Wrap the statements inside your program() function within a Promise, and upon completion of the asynchronous call, resolve or reject based on the result it gives.
Here's your function with Promises:
function program(id) {
return new Promise(function (resolve, reject) {
try {
var database = firebase.database();
var ref = database.ref("users/" + id + "/");
ref.on('value', function (user) {
if (typeof user.val().name === 'undefined') {
resolve(null);
} else {
console.log(user.val().name);
resolve(user.val().name);
}
})
} catch (e) {
reject(e)
}
});
}
And then, here's how you can read the result:
program(id).then(function (result) {
console.log(result)
//Do what you want with the result here
}).catch(function (error) {
console.log(error)
})
Note: You're executing this block in a for-each statement. If you're using Promises, you'd also need to look into how to use Promises inside a loop. For reference, check Promise.all()

Most likely you are trying to use the returned name in the code that calls your program function. E.g.
var name = program("1234");
console.log(name); // this will print undefined
This will not work, since your program() is not actually returning name. Data is loaded from Firebase asynchronously. By the time program() exits, the data isn't loaded yet.
This is easiest to see by putting a few log statements into the code:
function program (id) {
var database = firebase.database();
var ref = database.ref("users/" + id + "/");
console.log("Before attaching listener");
ref.on('value',function(user){
console.log("Got value from database");
})
console.log("After attaching listener, exiting function");
}
This will print:
Before attaching listener
After attaching listener, exiting function
Got value from database
This is likely not the order that you expected, but it is working as designed. Instead of waiting for the data to be loaded (and making the browser/user wait), your code continues. Then when the data is loaded, your callback is invoked. But in your original code that means that your return statement is unable to return the name to the original caller.
This is precisely the reason why the Firebase Database (and most web APIs) use callbacks like the one you pass into on(). This callback is invoked when the data is available and is the only place where you can access the user data. So any code that requires the data you just loaded must be inside that callback, or be called from inside that callback. E.g.
function program (id) {
var database = firebase.database();
var ref = database.ref("users/" + id + "/");
ref.on('value',function(user){
if (typeof user.val().name === 'undefined') {
return null;
}
else {
console.log(user.val().name);
appendToHtmlElement(user.val().name);
}
})
}

Firebase> DataBase> Role
Have you changed the value of rules?
Comment Example!
That can get the value after moving to name.
var ref = database.ref ("users/" + id + "/name");
ref.on ('value', function (user) {
    if (user.val ()! = null) {
         console.log (user.val ())
     }
}
If not, let's worry about it.

You should receive the returned value.
var name = ref.on('value',function(user){
if (typeof user.val().name === 'undefined') {
return null;
}
else {
console.log(user.val().name); //this doesnt show undefined
return user.val().name; //this shows undefined when appended to a html element
}
})
then use return name to get the value. or simply return the return ref.on('value' ...

JavaScript function response and chained promises

I have a Parse CloudCode beforeSave function, which roughly does the following:
Runs a query to check if there's a duplicate user to the one being saved;
If there is NO duplicate, I call a response.success(), which means the code can go ahead and allow saving the new user;
If, however, there is a duplicate, I want to take the existing user, fetch a group object and add the existing user to the group.
For this purpose, I am using chained promises to make the code cleaner. The code is below:
Parse.Cloud.beforeSave("Contact", function(request, response) {
var facebookID = request.object.get("facebookID");
var email = request.object.get("email");
var queryFb;
if (facebookID) {
queryFb = new Parse.Query(Parse.User);
queryFb.equalTo("facebookID", facebookID);
}
var queryEmail;
if (email) {
queryEmail = new Parse.Query(Parse.User);
queryEmail.equalTo("email", email);
}
var query;
if (facebookID && email) {
query = new Parse.Query.or(queryFb, queryEmail);
} else if (facebookID) {
query = queryFb;
} else {
query = queryEmail;
}
var user;
query.first().then(function(user) {
if (!user) {
response.success();
} else {
var groupQuery = new Parse.Query("Group");
groupQuery.equalTo("title", "ssAll");
groupQuery.equalTo("owner", request.user);
return groupQuery.first();
}
}).then(function(group) {
group.addUnique("contacts", user);
return group.save();
}).then(function(success) {
response.error("NOT ERROR - new object was NOT created");
}, function(error) {
response.error(error);
});
});
In my test case, the query returns !user, so the response.success() message is called - all good. However, this response seems to then travel down the promise chain, which is intended for the case when the query returns a user object. And so, my function terminates with an error on line group.addUnique("contacts", user); because, obviously, the group object is undefined.
How do I work around this issue?

The code needed a few improvements. The key improvement was to provide consistent starting conditions to the second promise's resolution (the second then block). The OP code called response.success() in the case where there was no existing user. This is fine, except the execution still falls through to the next resolution, in one case with an undefined group parameter.
The new code fixes that by returning either the existingUser (after the group has been updated) or null. Null tells the next promise resolution to call success() and allow the save to proceed, otherwise, block the save.
Also note, it is a mistake for the first block's user parameter to conflict with the var user in the enclosing scope. I tried to use variable naming below to highlight the two different types of users the code considers...
Parse.Cloud.beforeSave("Contact", function(request, response) {
var facebookID = request.object.get("facebookID");
var email = request.object.get("email");
// moved into a function so we can test and deal with it tersely
findUserByEmailOrFB(email, facebookID).then(function(existingUser) {
return (existingUser)? addContactToGroupOwnedBy(request.user, existingUser) : null;
}).then(function(existingUser) {
if (existingUser) {
response.error("NOT ERROR - new object was NOT created");
} else {
response.success();
}
}, function(error) {
response.error(error);
});
});
// find the group owned by ownerUser, add contactUser to its contacts return a promise fulfilled as contactUser
function addContactToGroupOwnedBy(ownerUser, contactUser) {
var groupQuery = new Parse.Query("Group");
groupQuery.equalTo("title", "ssAll");
groupQuery.equalTo("owner", ownerUser);
return groupQuery.first().then(function(group) {
group.addUnique("contacts", contactUser);
return group.save().then(function() { return contactUser; });
});
}
function findUserByEmailOrFB(email, facebookID) {
var queryFb;
if (facebookID) {
queryFb = new Parse.Query(Parse.User);
queryFb.equalTo("facebookID", facebookID);
}
var queryEmail;
if (email) {
queryEmail = new Parse.Query(Parse.User);
queryEmail.equalTo("email", email);
}
var query;
if (facebookID && email) {
query = new Parse.Query.or(queryFb, queryEmail);
} else if (facebookID) {
query = queryFb;
} else {
query = queryEmail;
}
return query.first();
}

The problem is that you are always resolving the first promise regardless of whether checking for the user was successful (no such user yet) or not. However, actually you don't ever have to resolve the promise. I suggest you separate the error case like this:
query.first().then(function(user) {
if (!user) {
response.success();
} else {
addUserToGroup(request.user).then(function() {
response.error("NOT ERROR - new object was NOT created");
}, function(error) {
response.error(error);
});
}
});
function addUserToGroup(user) {
var groupQuery = new Parse.Query("Group");
groupQuery.equalTo("title", "ssAll");
groupQuery.equalTo("owner", user);
return groupQuery.first().then(function(group) {
group.addUnique("contacts", user);
return group.save();
});
}
As you can see, the first promise doesn't ever have to be resolved because the result is not used anyway.

make async.waterfall start with argument from another function

I have bumped into a problem that I can't seem to solve. This is for a steam trading bot and it works well except for when two people trades with it at the same time because class_id and other_id are global variables and they will change in the middle of a trade if more than one is using it.
I tried defining the variables inside the last if statement but then get_class_id did not find the variables. Is there any way the async function can take item.classid and convert_id_64(offer.accountid_other) directly without defining them as variables? I appreciate any help.
var class_id
var other_id
function accept_all_trades(offers_recieved) {
offers_recieved.forEach( function(offer) {
if (offer.trade_offer_state == 1) {
if (typeof offer.items_to_give === "accept") {
offers.acceptOffer({tradeOfferId: offer.tradeofferid}, function(error, response) {
console.log('accepterat offer');
offer.items_to_receive.forEach(function(item) {
if (item.appid === '420') {
class_id = item.classid;
other_id = convert_id_64(offer.accountid_other);
console.log(class_id);
async.waterfall([get_class_id, get_stack, get_name, get_save], add_names);
}
});
});
}
}
});
}
function get_class_id(callback) {
var test = class_id
callback(null, test)
}
Update
I've changed the code to what ben suggested but still when I call get_class_id and try to print the id it is just a blank row in the console, any Ideas?
function get_class_id(callback) {
console.log(class_id);
var test = class_id;
callback(null, test)
}

The problem here is not aysnc.waterfall(). It's async calls (offers.acceptOffer(), get_class_id, get_stack, get_name, get_save, add_names) inside regular javascript forEach(). You need control-flow loops that can control the flow of those async calls. Here is the revised code using async.each():
function accept_all_trades(offers_recieved) {
async.each(offers_recieved, function(offer, eachCb) {
if (offer.trade_offer_state !== 1 || typeof offer.items_to_give !== "accept") {
return eachCb(null);
}
offers.acceptOffer({tradeOfferId: offer.tradeofferid}, function(error, response) {
console.log('accepterat offer');
async.each(offer.items_to_receive, function(item, eachCb) {
var class_id;
var other_id;
if (item.appid !== '420') {
return eachCb(null);
}
class_id = item.classid;
other_id = convert_id_64(offer.accountid_other);
console.log(class_id);
async.waterfall([
function(waterfallCb) {
var test = class_id;
console.log(class_id);
waterfallCb(null, test);
},
get_stack,
get_name,
get_save,
add_names
], eachCb);
}, function(err) {
console.log(err);
eachCb(null);
});
});
});
}