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nodejs file line count returning undefined


nodejs file line count returning undefined

By : Sashka Sashka
Date : November 21 2020, 04:03 PM
Hope this helps Your "get_line_count" is complete before file read operations even started. It's async IO, if that can help consider naming your function "start_file_linecount_sequence(name, oncomplete)" - the function puts some requests in the queue and exits (almost immediately) and your handler is called from event loop at some point of time later.
code :
function get_line_count(file, cb) {
    var count = 0;
    fs.createReadStream(file)
        .on('data', function(chunk) {
            for (var i = 0; i < chunk.length; i++)
                if (chunk[i] == 10) count++;
        })
        .on('end', function() {
            cb(null, count)
        })
        .once('error', cb);
}

get_line_count('test.txt', console.log);


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Reading a text file and returning the word count by line in C++

Reading a text file and returning the word count by line in C++


By : user3475951
Date : March 29 2020, 07:55 AM
hop of those help? You can have your map store most anything as a key's value. To have the capability of counting the number of times a word appears and keeping a dynamic list of the line numbers that it appears on you can do the following. This is the simplest straightforward solution that came to me, it is not the most efficient.
Use a map with a string key and value vector to store, index = WordLine, value at index = Count
code :
#include <vector>       // std::vector

using namespace std;
map<string, vector<int>> words;
#include <sstream>
using namespace std;

string line;
string word;
int line_num = 0;
while (getline(cin, line)) {
    istringstream words_iss(line); 
    while(line >> word) {
        ++words.at(word)[line_num];
    }
    ++line_num;
}
map<string, map<int, int>> 
undefined value returning while executing sql query in nodejs

undefined value returning while executing sql query in nodejs


By : Thomas
Date : March 29 2020, 07:55 AM
I wish this help you You misunderstand how asynchronous calls are make.
What happens when you run this part of code?
code :
     for(var i=0;i<rows.length;i++)
     {   
       var shopIdFetched = rows[i].shopId;
       client.connection.query(...) //these are asynchronous methods    
     }
        if(data.length > 0){
             console.log(rows[i],data);
        }
for(var i=0;i<10;i++)
{
    x(i);
}

function x(i){
    console.log(i);
    //this i will be same even after asynchronous paradighm
}
for (var i = 0; i < 10; i++) {
    (function(i){
        console.log(i);
    })(i)
}
 for(var i=0;i<rows.length;i++)
 {   
   (function(i){
   var shopIdFetched = rows[i].shopId;
    client.connection.query('select * from image where shopId=?',shopIdFetched,function(err,data){
       if(data.length > 0){
        console.log(rows[i],data);
        }

    });
    })(i);
 }
 for(var index=0;index<rows.length;index++)
 {   
   (function(i){
   var shopIdFetched = rows[i].shopId;
    client.connection.query('select * from image where shopId=?',shopIdFetched,function(err,data){
       if(data.length > 0){
        console.log(rows[i],data);
        }

    });
    })(index);
 }
Returning Then as Undefined. Q in NodeJS

Returning Then as Undefined. Q in NodeJS


By : Hai Yuan
Date : March 29 2020, 07:55 AM
this one helps. Your main function landingPage is not returning a value. The code inside it produces a promise, but you should also return it.
As you want to return the promise held by deferred, you should make deferred a variable that is defined in the outer function scope, so you can return the promise defined by it (deferred.promise):
code :
var landingPage = function (dir) {
    var deferred = Q.defer(); // *** define here
    Uni.get('https://'+getDirectory(dir).url)
        .header('Content-Type','text/html')
        .end(function (lp_data) {
            var europe = []; // *** define here, before the `if`
            if (lp_data.raw_body) {
                var $ = cheerio.load(lp_data.raw_body),
                    cn_europe = $('#location_europe .list-countries li'),
                    cn_asia = $('#content-location_asia_pacific li'),
                    cn_north_america = $('#content-location_north_america li');

                // Get Europe Company List
                for (var i = 0; i < cn_europe.length; i++) {
                    var country_name = $(cn_europe[i]).find('a').html().split('(')[0].trim(),
                        esomar_url = 'https://' + getDirectory(dir).url + '/' + $(cn_europe[i]).find('a').attr('href');
                    europe.push({country_name: country_name, esomar_url: esomar_url});
                }
            }
            // *** Move this out of the above `if`, so you always resolve/reject:
            return europe.length ? deferred.resolve(europe) : deferred.reject(err);
        });
    // *** return the promise (it will not be resolved yet, but that is the idea):
    return deferred.promise;
}
var landingPage = function (dir) {
    // return the promise that will now come from this chain:
    return Uni.get('https://'+getDirectory(dir).url)
        .header('Content-Type','text/html')
        .end()
        .exec() // turn request object to a promise
        .then(function (lp_data) {
            var europe = []; // *** define here, before the `if`
            if (lp_data.raw_body) {
                var $ = cheerio.load(lp_data.raw_body),
                    cn_europe = $('#location_europe .list-countries li'),
                    cn_asia = $('#content-location_asia_pacific li'),
                    cn_north_america = $('#content-location_north_america li');

                // Get Europe Company List
                for (var i = 0; i < cn_europe.length; i++) {
                    var country_name = $(cn_europe[i]).find('a').html().split('(')[0].trim(),
                        esomar_url = 'https://' + getDirectory(dir).url + '/' + $(cn_europe[i]).find('a').attr('href');
                    europe.push({country_name: country_name, esomar_url: esomar_url});
                }
            }
            // *** Return the data. Throw an error if to be rejected
            if (!europe.length) throw "no data!!";
            return europe;
        });
}
Module functions returning undefined in nodejs

Module functions returning undefined in nodejs


By : user3663505
Date : March 29 2020, 07:55 AM
it fixes the issue I am trying to return a value from module function and calling that function from different file, the function executes but return undefined , EDITED
You have to use the promise and thenable function.
code :
 student.get('/ranking',(req,res)=>{
    teacher_con.getClassid(req).then(res =>{
        console.log(classid);  //you will get the doc
    });
 });
    teacherController.getClassid = (req)=> { //use Promise
        return new Promise((resolve, reject)=>{
            Teacher.findOne({token:req.session.user})
            .exec((err, doc)=>{
                if(err){
                    reject(err);
                }
                else{
                    resolve(doc);
                }

            })
        });
    }
NodeJS Function returning undefined

NodeJS Function returning undefined


By : Liziyao
Date : March 29 2020, 07:55 AM
hope this fix your issue I have a function that needs to get data from another function, but the second one is returning undefined and i don't know why. , your companysList function doesn't return anything
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