Using Bootstrap alerts with Express.js 4

It’s often handy to be able to display a notification to users, noting a successful operation for example, or showing errors.

With Express this is normally done using a “flash message”. You’ll need the connect-flash middleware, as it was unbundled in Express 3.

var express = require('express'),
    flash = require('connect-flash'),
    app = express();

app.use(flash());
app.use(function(req, res, next){
    res.locals.success = req.flash('success');
    res.locals.errors = req.flash('error');
    next();
});

The 2nd piece of middleware ensures that flash messages will be available to the template as locals.

router.get('/account/name', function (req, res) {
        var data = {
            firstName: req.user.firstName,
            lastName: req.user.lastName
        };
        res.render('settings_name', data);
    });

    router.post('/account/name', function (req, res) {
        req.user.updateName(req.user.id, req.body.firstName, req.body.lastName, function(err) {
            if (err) {
                req.flash('error', 'Could not update your name, please contact our support team');
            } else {
                req.flash('success', 'Your name was updated');
            }
            res.redirect('/account/name');
        });
    });

The final step is to display the messages when necessary. Bootstrap alerts provide an easy way to do this:

doctype html
html
  head
    link(rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap.min.css")
  body
    if error && error.length > 0
      .alert.alert-danger.alert-dismissible.fade-in(role="alert")
        button.close(type="button" data-dismiss="alert" aria-label="Close")
          span(aria-hidden="true") ×
        p= error
    if success && success.length > 0
      .alert.alert-success.alert-dismissible.fade-in(role="alert")
        button.close(type="button" data-dismiss="alert" aria-label="Close")
          span(aria-hidden="true") ×
        p= success

    script(src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js")
    script(src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js")

3 thoughts on “Using Bootstrap alerts with Express.js 4

  1. Kevin Ilsen February 3, 2018 / 2:13 pm

    I’ve been doing it this way (as described in the article) for quite some time, and I discovered that the flash messages are lost on redirect. So instead of this:

    app.use(function(req, res, next){
    res.locals.success = req.flash(‘success’);
    res.locals.errors = req.flash(‘error’);
    next();
    });

    I now do this:

    // middleware for all views
    app.use((req, res, next) => {
    // Pass the flash prototype; the templates will use it to get the messages
    // (this works with redirect)
    res.locals.flash = req.flash;
    next();
    });

    Then in my views (I use EJS templating), wherever I want to show the flash messages, I include a ‘partial’ that looks like this:


  2. Kevin Ilsen February 3, 2018 / 2:14 pm

    Hmm. It’s not allowing me to post the contents of the EJS.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s