How to handle a get request with node.js (express)

Question

I'm a node.js newbie and I'm creating my first big app with it (I'm using express). I need to have my webpage perform some javascript canvas-drawing when the user loads an id with a get request, e.g.

www.mywebsite.com/page?id=22

I know I can handle this with a simple

var express        =        require("express");
var app            =        express();
app.get('handle',function(request,response){
    //request.id
});

but I don't know how to start my webpage with the asked drawing for that id. Every tutorial on the internet on express and get explains how to handle get requests... well this question is about "what happens next?"

Rephrased: I'm not sure how should I tell the html page "you need to draw what is associated with this id" from express and then send that page back to the user.

Answer 1

You can take the id from params and after this to return a response based on that id.

var express = require('express');
var app = express();

app.get("/page/:id",function(request, response){
    var id = request.params.id;
    // do something with id
    // send a response to user based on id
    var obj = { id : id, Content : "content " +id };

    response.writeHead(200, {"Content-Type": "application/json"});
    response.write(JSON.stringify(obj));
});

Notes:

1. You use /page/:id to make urls like www.mywebsite.com/page/22 or www.mywebsite.com/page?id=22 and you can have acces to id on server with request.params.id (output: 22).

2. With response you can write a response to the server. In this example i returned a json object.

3. In writeHead 200 come from status which means OK , and content-type means that I return a json object

4. You can return what you want, a page or something else, this is just an example (PoC).

Answer 2

If you want to pass multiple variables in the request, you can pass it in the following way:

var emailVar = "someEmail@gmail.com";
var nameVar = "someName";
var url = `/home?email=${emailVar}&name=${nameVar}`;
//Now make the request.

and in the backend logic, you can retrieve these values as:

app.get('/home', function(request, response)
{
    console.log(request.query.email+"  "+request.query.name);
    var email = request.query.email;
    var name = request.query.name;
    response.setHeader('Content-Type', 'application/json');
    if(request.query.email)
    {
        response.send(JSON.stringify({
            message: 'Got the email'
        }));
    }
    else
    {
        response.send(JSON.stringify({
            message: 'No email sent'
        }));
    }
});

This approach is useful for performing query operations in the backend.