Activate Node function on action

Question

Activate Node function on action

1.1k Views Asked by user137717 At 04 April 2025 at 09:57

I'm new to Node. Most of my server consists of require statements, middleware and things like

app.get('/page.html', function (req, res, next){
    res.render("page.html");
});

How do I trigger a function from a button click on my web page? Does the entire server script run on each connection, like from the require statements to the end?

Original Q&A

There are 2 best solutions below

**Zlatko** · Answer 1

Triggering an action on click is something that front end usually needs to initiate. You would fire an Ajax request to one of your backend routes. Let's day you have a route like

var successfulCalls = 0;    
app.get('/my-action', function(req, res) {

     // you can do your action here
     //like calling a database or something
     // then you need to, eventually, close the request.
     db.get('somedata')
     .then(function(results) {

         res.json(results);
         successfulCalls++;
     })
     // also handle errors
     .catch(function(err) {
         res.status(500);
         res.end();
      });
});

There are three functions in there. Express will hold on to them, save refs to them somewhere.

When a request comes in, when it matches the /my-action, it will call the first function. And each time the request matches the url, this function will get called.

The second function will only get called when the db call is successful, the third one when db fails.

So on each request, only a few predefined functions will run. And you can even save some state between requests, like logging successful calls.

I hope this makes sense, because my thumbs hurt now :-)

**Avaq** · Answer 2

Does the entire server script run on each connection, like from the require statements to the end?

No.

A Node application is a continues process. When you start it the script will run, including the require statements, and during that time (the startup time) you will declare state and register callbacks (which is what you're doing with app.get(..) for example).

After the startup time, the application will continue running for as long as there are callbacks waiting for events. In a web-server, that's probably forever because you're always waiting for a "request" event. When the request event triggers (because of an incoming connection), callbacks (like the one from your example) will be called and that's the only thing that runs again and again on each connection.

How do I trigger a function from a button click on my web page?

The JavaScript that is executing on the page (and thus able to respond to user "clicks" and such) is not the same JavaScript that runs on your server (in Node). In order to have JavaScript execute on the client (the browser) you have to include it in the HTML page:

<head>
  <script type="text/javascript" src="http://my-server.example.com/client-script.js"></script>
</head>

And host it on your server:

app.get('/client-script.js', function(req, res){
  res.sendFile('assets/client-script.js');
});

In that script you would handle a button press. If you want to let the server know that the button was pressed, you'd have to send another request to the server. Either by redirecting the user to another page, or sending an AJAX request. You then have to have another route on your server that listens to that specific request, for example:

app.post('/button-was-pressed', function(req, res){
  console.log('We have a winner.');
});

Activate Node function on action

There are 2 best solutions below

Related Questions in NODE.JS

Related Questions in HTTPSERVER

Trending Questions

Popular # Hahtags

Popular Questions