javascript - Function should return string when called, but returns undefined instead -


this question has answer here:

background

i'm using node.js build small app reads weather data api. i'm using 2 files called router.js , weather.js.

router.js deals routes related web application (e.g. www.myappdomain.com/routeexample).

weather.js interacts weather api , has functions weather data, parses data, , formulates readable string.

router.js

here code in router.js:

const express = require("express"); const router = express.router(); const weather = require("./weather");  router.get('/', (req, res) => {   const {location} = req.query;   console.log(location); // prints query submitted user   let weatherstring = weather.getweatherdata(location);   console.log(weatherstring); // returns undefined   res.render("index", weatherstring);   res.end(); });  module.exports = router;

inside of callback function request, can see location variable outputs correct string. however, when calling getweatherdata function using location variable argument, returns undefined value.

weather.js

now let's take inside of weather.js see getweatherdata function looks like. i've excluded of code conciseness.

function printweather(location, temperature) {   let string = `the weather ${location} ${temperature} degrees celcius.`;   return string; }  function parseweatherdata(weatherdata) {   let locationstring = weatherdata.name + ", " + weatherdata.sys.country;   let temperature = weatherdata.main.temp;   printweather(locationstring, temperature); } function getweatherdata(location) {    const request = http.get(`http://api.openweathermap.org/data/2.5/weather?q=${location}&appid=${api["key"]}&units=metric`, response => {     if (response.statuscode === 200) {       let body = "";       response.on("data", (data) => {         body += data.tostring();       });       response.on("end", () => {         const weatherdata = json.parse(body);;         parseweatherdata(weatherdata);       });     }   }); }  module.exports.getweatherdata = getweatherdata;

as can see, when getweatherdata called in router.js, starts executing getweatherdata calls parseweatherdata function. when parseweatherdata gets executed, calls printweather function. printweather function stores readable string in variable , function returns string.

my problem string gets created isn't being returned router.js when getweatherdata function called.

what i've tried

i've been troubleshooting getweatherdata, parseweatherdata, , printweather functions console.log statements, , outputting correct values inside of weather.js. trouble returning final string inside of printweather router.js.

http.get asynchronous call. pass in function callback getweatherdata , call when response complete.

weather.js

function printweather(location, temperature) {    let string = `the weather ${location} ${temperature} degrees celcius.`;    return string;  }    function parseweatherdata(weatherdata) {    let locationstring = weatherdata.name + ", " + weatherdata.sys.country;    let temperature = weatherdata.main.temp;    return printweather(locationstring, temperature);  }  function getweatherdata(location, done) {     const request = http.get(`http://api.openweathermap.org/data/2.5/weather?q=${location}&appid=${api["key"]}&units=metric`, response => {      if (response.statuscode === 200) {        let body = "";        response.on("data", (data) => {          body += data.tostring();        });        response.on("end", () => {          const weatherdata = json.parse(body);;          const formattedweather = parseweatherdata(weatherdata);          done(null, formattedweather);        });      }    });  }    module.exports.getweatherdata = getweatherdata;

router.js

const express = require("express");  const router = express.router();  const weather = require("./weather");    router.get('/', (req, res) => {    const {location} = req.query;    /*second argument getweatherdata anonymous function. err node convention, result second argument in callback */    weather.getweatherdata(location, (err, weatherstring) => {      res.render("index", weatherstring);      res.end();    });  });    module.exports = router;


Comments

Post a Comment

Popular posts from this blog

android - InAppBilling registering BroadcastReceiver in AndroidManifest -

i'm implementing inapp billing in android app. works well, however, i'm trying decouple broadcast receiver activity manifest. suggestion in android's trivialdrive sample: // important: dynamically register broadcast messages updated purchases. // register receiver here instead of <receiver> in manifest // because call getpurchases() @ startup, therefore can ignore // broadcasts sent while app isn't running. // note: registering listener in activity bad idea, done here // because sample. regardless, receiver must registered after // iabhelper setup, before first call getpurchases(). currently there's class extends broadcastreceiver : public class iabbroadcastreceiver extends broadcastreceiver { /** * intent action receiver should filter for. */ public static final string action = "com.android.vending.billing.purchases_updated"; private final iabbroadcastlistener mlistener; public iabbroadcastreceiver(iabbroadcastlistener listener) { m...
Read more

python Tkinter Capturing keyboard events save as one single string -

is possible store keyboard events 1 string? code below stores 1 char , prints it. card reader or bar code reader, contains collection of character/ string not 1 character @ time. goal save char pressed text variable. from tkinter import * root = tk() def key(event): text= event.char text+= event.char print ("pressed", text) def callback(event): frame.focus_set() print ("clicked at", event.x, event.y) frame = frame(root, width=100, height=100) frame.bind("<key>", key) frame.bind("<button-1>", callback) frame.pack() root.mainloop() currently, creating text variable , everytime key() function gets called, , text stores last character typed. you can define text module level variable , , use module level text inside key function - text = '' def key(event): global text text+= event.char print("pressed", text)
Read more

sql server - Why does Linq-to-SQL add unnecessary COUNT()? -

here tables: create table customer ( cid int primary key, name varchar(32) ) create table ord ( oid int primary key, cid int foreign key references customer, address varchar(20) ) here's linq-to-sql statement: var aaa = c in db.customer select new { c, o = c.ord.tolist() }; and here's inexplicable query generated linq-to-sql: select [t0].[cid] [cid], [t0].[name] [name], [t1].[oid] [oid], [t1].[cid] [cid2], [t1].[address] [address], (select count(*) [dbo].[ord] [t2] [t2].[cid] = [t0].[cid]) [value] [dbo].[customer] [t0] left outer join [dbo].[ord] [t1] on [t1].[cid] = [t0].[cid] order [t0].[cid], [t1].[oid] i want understand how rid of count(*) part. it's entirely uncalled for! linq needs count(*) in order determine number of entries returned o = c.ord.tolist() .
Read more