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JS For loop is just not iterating, Why?

So, I am making this discord bot and I wanted to make it so if someone's message gets deleted, It can be stored onto a .txt file, And if someone wanted, They could just type in a command and the bot will show the list of deleted messages.
So, when the command is fired, it will need a number parameter and that parameter will be the number of messages that will be shown.
Let's call that number numberOfSnipes
The code will get the .txt file and turn it into an array by splitting each line and putting it in one array.
As so,
fs.readFile('deletedMsgs/' + message.guildId + '.txt', function (err, data) {
messagesArray = data.toString().split('\n');
});
As the code says, It will be called messagesArray
Now the problem comes here, We will need to iterate through the array and get the number of messages needed, This will be put into another array which will be called messagesToShow
So, I tried coding that and failed,
Code:
messagesToShow = []
for (let i = messagesArray.length; i < messagesArray.length - numberOfSnipes; i--) {
console.log(i)
messagesToShow.push(messagesArray[i])
}
FYI, console.log(i) did not log anything.
I tried to log messagesArray, It logged an empty array
Keep in mind that numberOfSnipes and messagesArray were both logged and they returned the right information.
Since, This can be more easier for you all. To solve, I will provide the whole code:
if (message.content.toLowerCase().startsWith(config.prefix + 'snipelist')) {
numberOfSnipes = parseInt(message.content.split(' ')[1]);
if (fs.existsSync('deletedMsgs/' + message.guildId + '.txt')) {
fs.readFile(
'deletedMsgs/' + message.guildId + '.txt',
function (err, data) {
messagesArray = data.toString().split('\n');
console.log(messagesArray);
if (numberOfSnipes > messagesArray.length) {
message.reply('Unable to return messages.');
} else {
messagesToShow = [];
for (
let i = messagesArray.length;
i < messagesArray.length - numberOfSnipes;
i--
) {
console.log(i);
messagesToShow.push(messagesArray[i]);
}
console.log(messagesToShow);
finalMessage = ' ';
for (let letter in messagesToShow.toString()) {
if (letter != ',') {
finalMessage += letter;
} else if (letter == ',') {
finalMessage += '\n';
}
}
message.reply(finalMessage);
}
}
);
}
}
Any help is appreciated.

How can I run recursive function in cypress or find length with async await

I am running tests using Cypress.
I have an array of Litecoin addresses. I am trying to set first in the input. Then submit the form.
If the address is duplicate then a notification is displayed and submit button will be not visible. The same I want to set for the second element and so on till end of the array.
I tried recursive function:
function runTillElementFound (totalCount, currentCount, litecoin_addresses)
{
var self = this;
if (currentCount < totalCount) {
return cy.get('body').then(($body) =>
{
if ($body.find(dash_page.save_wallet_circle_btn)) {
//if there is save button then set address and submit form
cy.log('taken address: ' + litecoin_addresses[ currentCount ]);
dashact.fill_wallet(litecoin_addresses[ currentCount ]);
cy.log('address is filled');
dashact.submit_wallet(true, 0);
self.runTillElementFound(totalCount, currentCount++);
}
});
} else {
return false; //if element not present after Max count reached.
}
I try to call it:
it('Set wallet', () =>
{
cy.log('this is array length: ' + litecoin_addresses);
runTillElementFound(20, 0, litecoin_addresses);
/* comact.submit_form(true, 1);
let ltc_address = promisify(dashact.get_wallet_value());
cy.log('this is address: ' + ltc_address);
//close popup and check that it is closed:
popact.submit_payment(); */
});
However I receive undefined:
I have also tried non recursive function:
for (var i = 0; i < litecoin_addresses.length; i++) {
cy.log('taken address: ' + litecoin_addresses[ i ])
if (litecoin_addresses[ i ] == wallet_before_edit || litecoin_addresses[ i ].length == 0 || litecoin_addresses[ i ].startsWith('ltc')) {
continue;
}
else {
cy.log('this is curent i: ' + i);
dashact.fill_wallet(litecoin_addresses[ i ]);
dashact.submit_wallet(true, null);
cy.get('body').then(($body) =>
{
// synchronously query from body
// to find which element was created
if ($body.find(com_page.not_message).length) {
// error was found, do something else here
cy.log('error was found');
}
else {
cy.log('error not found');
// input was not found, do something else here
i = litecoin_addresses.length;
cy.log('current i value: ' + i);
}
})
}
However it for sure, does not work, as i inside promise has one valued but in the loop it still remains the same.

If you use a specific array in your test code, you can easily get the length of the array by using the .lenght and access its elements by using the for loop.

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' ...

How can I throttle stack of api requests?

I have an array of ids, and I want to make an api request for each id, but I want to control how many requests are made per second, or better still, have only 5 open connections at any time, and when a connection is complete, fetch the next one.
Currently I have this, which just fires off all the requests at the same time:
_.each([1,2,3,4,5,6,7,8,9,10], function(issueId) {
github.fetchIssue(repo.namespace, repo.id, issueId, filters)
.then(function(response) {
console.log('Writing: ' + issueId);
writeIssueToDisk(fetchIssueCallback(response));
});
});

Personally, I'd use Bluebird's .map() with the concurrency option since I'm already using promises and Bluebird for anything async. But, if you want to see what a hand-coded counter scheme that restricts how many concurrent requests can run at once looks like, here's one:
function limitEach(collection, max, fn, done) {
var cntr = 0, index = 0, errFlag = false;
function runMore() {
while (!errFlag && cntr < max && index < collection.length) {
++cntr;
fn(collection[index++], function(err, data) {
--cntr;
if (errFlag) return;
if (err) {
errFlag = true;
done(err);
} else {
runMore();
}
});
}
if (!errFlag && cntr === 0 && index === collection.length) {
done();
}
}
runMore();
}

With Bluebird:
function fetch(id) {
console.log("Fetching " + id);
return Promise.delay(2000, id)
.then(function(id) {
console.log(" Fetched " + id);
});
}
var ids = [1,2,3,4,5,6,7,8,9,10];
Promise.map(ids, fetch, { concurrency: 3 });
<script src="https://cdnjs.cloudflare.com/ajax/libs/bluebird/3.3.1/bluebird.min.js"></script>
<!-- results pane console output; see http://meta.stackexchange.com/a/242491 -->
<script src="http://gh-canon.github.io/stack-snippet-console/console.min.js"></script>

Divide your data into as many arrays as you want concurrent connections. Schedule with setTimeout, and have the completion callback handle the rest of the sub-array.
Wrap the setTimeout in a function of its own so that the variable values are frozen to their values at the time of delayed_fetch() invocation.
function delayed_fetch(delay, namespace, id, issueIds, filters) {
setTimeout(
function() {
var issueId=issueIds.shift();
github.fetchIssue(namespace, id, issueId, filters).then(function(response) {
console.log('Writing: ' + issueId);
writeIssueToDisk(fetchIssueCallback(response));
delayed_fetch(0, namespace, id, issueIds, filters);
});
}, delay);
}
var i=0;
_.each([ [1,2] , [3,4], [5,6], [7,8], [9,10] ], function(issueIds) {
var delay=++i*200; // millisecond
delayed_fetch(delay, repo.namespace, repo.id, issueIds, filters);
});

i'd recommend using throat just for this: https://github.com/ForbesLindesay/throat

Using Bluebird
function getUserFunc(user) {
//Get a collection of user
}
function getImageFunc(id) {
//get a collection of image profile based on id of the user
}
function search(response) {
return getUsersFunc(response).then(response => {
const promises = response.map(items => return items.id);
const images = id => {
return getImagesFunc(id).then(items => items.image);
};
return Promise.map(promises, images, { concurrency: 5 });
});
}
Previously i used ES6 function Promise.all(), but it doesn't work like what i'm expecting. Then go with third party library bluebird.js and Work like a charm.

synchronic node js function

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.