Developing template engines for Express

Use the app.engine(ext, callback) method to create your own template engine. ext refers to the file extension, callback is the template engine function which accepts the location of the file, the options object, and the callback function, as its parameters.

The following is an example of implementing a very simple template engine for rendering “.ntl” files.

var fs = require('fs'); // this engine requires the fs module
app.engine('ntl', function (filePath, options, callback) { // define the template engine
  fs.readFile(filePath, function (err, content) {
    if (err) return callback(new Error(err));
    // this is an extremely simple template engine
    var rendered = content.toString().replace('#title#', '<title>'+ options.title +'</title>')
    .replace('#message#', '<h1>'+ options.message +'</h1>');
    return callback(null, rendered);
  })
});
app.set('views', './views'); // specify the views directory
app.set('view engine', 'ntl'); // register the template engine

Your app will now be able to render “.ntl” files. Create a file named “index.ntl” in the views directory with the following content.

#title#
#message#

Then, create the following route in your app.

app.get('/', function (req, res) {
  res.render('index', { title: 'Hey', message: 'Hello there!'});
})

On making a request to the home page, “index.ntl” will be rendered as HTML.