JavaScript automatic refresh

Question

it's my first time with JS and I'm doing task for my class. How can I set automatic refresh every n seconds in this type of code? Found some examples but none of them worked for me.

var http = require('http');
var port = 8080;

function lightSensor() {
   var data =  Math.random().toFixed(2)
   console.log("Light sensor: " + data);  
   return data;
}

http.createServer(function(req,res){
  res.writeHeader(200, {'Content-Type': 'application/json'});  
  res.write('{"Light sensor" : ' + lightSensor() + '}');      
  res.end();
}).listen(port);
console.log('Server listening on: http://localhost:' + port);

process.on('SIGINT', function () { 
  process.exit();
});

You could send a refresh header? https://stackoverflow.com/questions/283752/refresh-http-header — evolutionxbox, Jun 13 '21 at 12:33
You will probably need to set up the automatic refresh on the client-side. — evolutionxbox, Jun 13 '21 at 12:47
Ok my bad, you asked in the question that you want to refresh page so i thought you wanted to use it at client side since you didn't mention it, sorry my bad — Uzair Saiyed, Jun 13 '21 at 12:57

score 1 · Answer 1 · answered Jun 13 '21 at 12:51

Ant kind of delays inside an http request are not desirable.

Actually, you need to modify where you call this http server to repeat the http request every n seconds.

For example if you are calling this in JavaScript (inside a browser or nodejs) you can use setInterval to repeat the call:

setInterval(() => {
  fetch('localhost').then(res => console.log(res))
}, n * 1000)

Note that if the interval is lower then your server response time, the order of the output might not be the same as the requests. If you need to wait for the previous response before doing another request, you must use some more complex code to wait the previous request.

Amit Gupta · Answer 2 · 2021-06-13T12:44:32.410

0

You can use setTimeout javascript function for this. eg. If you want to call lightSensor function in very 5 sec then use below code -

setInterval(lightSensor, 5000);

edited Jun 13 '21 at 12:44

answered Jun 13 '21 at 12:34

Amit Gupta

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3
8

Why does this help here? the res has already been sent by that point? May you share an example using the code from the question? – evolutionxbox Jun 13 '21 at 12:34
There must be some code that you need to call every n second, right? Then call that function from setTimeout – Amit Gupta Jun 13 '21 at 12:36
(I am not the OP) - Why does calling `lightSensor` help here? It may call the function again, but the page has already been sent back to the browser. – evolutionxbox Jun 13 '21 at 12:40
1

setTimeout executes function only once after the specified time you have to use setInterval @Amit Gupta – Uzair Saiyed Jun 13 '21 at 12:43
Then your question and code given is incomplete, you need to give the complete detail. When http.createServer called? Which function you need to call in every n sec? – Amit Gupta Jun 13 '21 at 12:44
@sowiacz may you answer Amit's comment? – evolutionxbox Jun 13 '21 at 12:47

JavaScript automatic refresh

2 Answers2