i can't figure out why we are using response.on

Question

I've written a code here and I want to know what "response.on" is doing and why we are passing "data", what is this "data". what exactly that ".on" is used for.

const express = require("express");
const https = require("https");
const app = express();
app.get("/",function(req,res){
  const url="https://api.openweathermap.org/data/2.5/weather?q=London&appid=5c8618a9210a11846accc217f3b3084f";
  https.get(url,function(respons){
    response.on("data",function(data){
      const wht = JSON.parse(data)
      temp = wht.main.temp
      res.send("temp   "+ temp)
    })
  })
})
app.listen(3000, function(){
  console.log("running");
});

Answer 1

.on("nameOfEvent", callback) it's a event emitter. So, basically whenever that event is called, that callback will be executed. data is just the name of the event.

Answer 2

1. In your code there is bug.

You using respons in the argument of function and response inside of function.

2. Waiting on data of response is documented in https

https://nodejs.org/api/https.html#https_https_get_options_callback

You can read that response is not a classical response from the server but an event listener that listens for stream of data.

It is a low-level interface and in your applications, you should not use them. Lets interest in node-fetch or axios instead if you want only get a response, but not process streams in real-time.