when i try to use response.send() is always shows a message Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client.I have provided the code Pls help me to fix this error.
/**
* Post is used to create new items
* Put is used to update the items
* Listen is used to run the server
* Delete is used to delete an item
*/
const express = require('express');
const bodyParser = require('body-parser');
const axios = require('axios').default;
const { response } = require('express');
const app = express();
app.use(bodyParser.urlencoded({extended:false}));
app.use(bodyParser.json());
var city = 'delhi';
app.put('/enter_data',(req,res)=>{
city = req.body.City;
if(city === "" || !city){
res.status(500).send({error: "Write something"});}
else
{
res.send("Now you can see the temperature");
}
})
app.get('/show_temp',(req,res)=>{
var sample = "https://api.openweathermap.org/data/2.5/weather?q="+city+'&units=metric&appid=bb16c5275f7a3c1439973f71e4dc811f';
res.send("Running");
axios.get(sample)
.then(response => {
var t = "Temperature in "+city+" is "+String(response.data.main.temp)+"°C"
if(t)
{
res.status(200).send(t);
}
})
.catch(error => {
console.log(error);
//res.status(503).send({status: 1, message: "Messages not available!"});
})
});
app.listen(5000,()=>{
console.log("Port Running");
})
You cannot send a response to a request multiple times like this; One request should equate to one response.
app.get('/show_temp',(req,res)=>{
var sample = "https://api.openweathermap.org/data/2.5/weather?q="+city+'&units=metric&appid=bb16c5275f7a3c1439973f71e4dc811f';
res.send("Running"); // Here you are sending a response of "Running" to the client
axios.get(sample)
.then(response => {
var t = "Temperature in "+city+" is "+String(response.data.main.temp)+"°C"
if(t)
{
res.status(200).send(t); // Here is where you are sending you're actual response and thus triggering the error.
}
})
.catch(error => {
console.log(error);
//res.status(503).send({status: 1, message: "Messages not available!"});
})
});
Refactoring this, a solution would be:
app.get('/show_temp',(req,res)=>{
var sample = "https://api.openweathermap.org/data/2.5/weather?q="+city+'&units=metric&appid=bb16c5275f7a3c1439973f71e4dc811f';
axios.get(sample)
.then(response => {
var t = "Temperature in "+city+" is "+String(response.data.main.temp)+"°C"
if(t)
{
res.status(200).send(t);
}
})
.catch(error => {
console.log(error);
res.status(503).send({status: 1, message: "Messages not available!"}); // This is fine so long an error is not thrown AFTER the response
})
});
I will also note that there are definitely use cases for sending different response for different scenarios. You may have a validation step for example, where you need to send a 400 status to the client. In this case, you want to return your response to prevent other responses from being sent.
Example snippet:
if (badData) {
return res.sendStatus(400)
}
res.sendStatus(200)