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!
Related
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);
}
}
});
I have following function:
exports.onDataAdded = functions.database.ref('/Lager/Shafts/Rescue/582/582001').onWrite((change, context) => {
if (change.before.exists()) {
return null;
}
// Exit when the data is deleted.
if (!change.after.exists()) {
return null;
}
const original = change.after.val();
return change.after.ref('/Lager/Shafts/Rescue/583/583001').set(original);
});
I am trying to keep the count of product 1 equal to the count of product two (Can't put it in the same ID for several reasons). It executes the function and says the status is ok but does not update the new value of product 2.
What am I missing?
Please try this, Your function is exiting without executing the update.
exports.onDataAdded = functions.database.ref('/Lager/Shafts/Rescue/582/582001').onWrite((change, context) => {
if (change.after.exists()) {
const original = change.after.val();
return admin.database().ref('/Lager/Shafts/Rescue/583/583001').set(original);
}
// Exit when the data is deleted.
if (!change.after.exists()) {
return null;
}
});
This seems like a noop:
exports.onDataAdded = functions.database.ref('/Lager/Shafts/Rescue/582/582001').onWrite((change, context) => {
if (change.before.exists()) {
return null;
}
Or more precisely: it will only get past this code when you delete /Lager/Shafts/Rescue/582/582001, which is not what you seem to be trying. My guess is that you meant the inverse in your check:
if (!change.before.exists()) {
return null;
}
I use the recursive function below, in order to reopen website if httpstatus != 200:
retryOpen = function(){
this.thenOpen("http://www.mywebsite.com", function(response){
utils.dump(response.status);
var httpstatus = response.status;
if(httpstatus != 200){
this.echo("FAILED GET WEBSITE, RETRY");
this.then(retryOpen);
} else{
var thisnow = hello[variable];
this.evaluate(function(valueOptionSelect){
$('select#the_id').val(valueOptionSelect);
$('select#the_id').trigger('change');
},thisnow);
}
});
}
The problem is that sometimes the retryOpen function does not even go as far as to callback function(response){}. Then, my script freezes.
I wonder how one could change the function to be able to recursively try to open website again if there is no response from website (not even some error code as 404 or something)? In other words, how to rewrite the retryOpen function so it reruns when the function does not reach callback after a certain amount of time?
I would try something like this. Please note this is untested code, but should get you on the correct path
retryOpen = function(maxretry){
var count = 0;
function makeCall(url)
{
this.thenOpen(url, function(response){
utils.dump(response.status);
});
}
function openIt(){
makeCall.call(this,"http://www.mywebsite.com");
this.waitFor(function check() {
var res = this.status(false);
return res.currentHTTPStatus === 200;
}, function then() {
var thisnow = hello[variable];
this.evaluate(function(valueOptionSelect){
$('select#the_id').val(valueOptionSelect);
$('select#the_id').trigger('change');
},thisnow);
}, function timeout() { // step to execute if check has failed
if(count < maxretry)
{
openIt.call(this);
}
count++
},
1000 //wait 1 sec
);
}
openIt();
}
I'm trying to write a Parse.com Cloud Code function to accomplish the following workflow:
User submits a value.
Cloud code function checks to see if that value matches any objects of type code.
If not, the function returns a "not found" value.
If so, the object of type code is assumed to have a pointer to an object of type item.
Then, code.item is checked to see whether it has a pointer to an object of type alert.
If not, the function returns a "not found" value.
If code.item.alert does exist, then I want to fetch the full alert object, including pointers which may or may not exist, up to 2 layers deep.
As I begin writing the code for this function, I can get it working to the point of checking to see whether the code exists and, if so, whether code.item.alert also exists.
This is where the problem arises. As it currently stands, in the working version of my function, the alert item that is returned is only the class type and objectId. I understand why that is happening, and I am trying to write code to populate the object before returning it, but I am failing in that attempt.
Here's the code that is working so far (but only returning the alert object's shell):
Parse.Cloud.define("alertLookup", function (request, response) {
Parse.Cloud.useMasterKey();
var codeQuery = new Parse.Query("code");
codeQuery.equalTo("value", request.params.code);
codeQuery.include("item");
codeQuery.find().then(function (codes) {
if (codes.length === 0) {
response.success("no item");
} else {
var code = codes[0];
var item = code.get("item");
var alert = item.get("alert");
if (alert === null || alert === undefined) {
response.success("no item");
} else {
response.success(alert);
}
}
}, function (error) {
response.error(error);
});
});
Here's what I have tried that is failing with an error code of 141:
Parse.Cloud.define("alertLookup", function (request, response) {
Parse.Cloud.useMasterKey();
var codeQuery = new Parse.Query("code");
codeQuery.equalTo("value", request.params.code);
codeQuery.include("item");
codeQuery.find().then(function (codes) {
if (codes.length === 0) {
response.success("no item");
} else {
var code = codes[0];
var item = code.get("item");
var alert = item.get("alert");
if (alert === null || alert === undefined) {
response.success("no item");
} else {
return alert.fetch();
}
}
}).then(function (a) {
response.success(a);
}, function (error) {
response.error(error);
});
});
Why won't the fetch() call work properly? When I insert console.log() statements, although alert is non-null, return alert.fetch(); does not ever seem to be called. At least, the response.success(a); line is never called. Why not?
Try this instead while chaining Promises:
codeQuery.find().then(function (codes) {
if (codes.length != 0) {
var code = codes[0];
var item = code.get("item");
var alert = item.get("alert");
if (alert != null && alert != undefined) {
var alertObj = new Parse.Object("alert"); // alert class ???
alertObj.id = alert.id;
return alertObj.fetch();
}
}
// return a Promise for no items
return Parse.Promise.as("no item");
}).then(function (a) {
response.success(a);
}, function (error) {
response.error(error);
});
I am trying to write a polling method that polls a server periodically to check whether a zip file has already been created or not.
What I want to accomplish are the following:
Calls(ajax) an API that creates a zip file on server
Calls(ajax) another API that checks if the zip file has already been created (polling method)
Some subsequent process
Here is my code snippet ↓
var success: boolean = false;
//1. requests a server to create a zip file
this.apiRequest.downloadRequest(params,ApiUrl.URL_FOR_DOWNLOAD_REQUEST)
.then((resObj) => {
var apiRes: IDownloadService = resObj.data;
if (apiRes.status[0].statusCode == "000") {
success = true;
} else {
//Error
}
}).then(() => {
if (success) {
//2. polls the server to check if the zip file is ready
<- Polling method↓ ->
this.polling(params).then((zipUrl) => {
console.log(zipUrl); //always logs zipUrl
//some subsequent process...
});
}
});
Could anyone give some examples of polling method that would work in this case?
Added:
private polling(params: any): ng.IPromise<any> {
var poller = () => this.apiRequest.polling(params, ApiUrl.URL_FOR_POLLING);
var continuation = () => poller().then((resObj) => {
var apiRes: IDownloadService = resObj.data;
if (apiRes.zipFilePath == "") {
return this.$timeout(continuation, 1000);
} else {
return apiRes.zipFilePath;
}
})
var result: ng.IPromise<any> = continuation();
return result;
}
Basically abstract the methods out as shown below:
let poll = () => this.apiRequest.downloadRequest(params,ApiUrl.URL_FOR_DOWNLOAD_REQUEST)
let continuation = () => poll().then((/*something*/)=> {
/*if still bad*/ return continuation();
/*else */ return good;
})
continuation().then((/*definitely good*/));
Update
As requested in the comment below:
return this.$timeout(continuation, 1000);
This is needed to get angular to kick off a digest cycle.