---
layout: page
title: Developing template engines for Express
menu: advanced
lang: uz
description: Learn how to develop custom template engines for Express.js using app.engine(),
  with examples on creating and integrating your own template rendering logic.
---

# 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.

<pre><code class="language-javascript" translate="no">
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) throw 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
</code></pre>

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

<pre><code class="language-javascript" translate="no">
#title#
#message#
</code></pre>
Then, create the following route in your app.

<pre><code class="language-javascript" translate="no">
app.get('/', function (req, res) {
  res.render('index', { title: 'Hey', message: 'Hello there!'});
});
</code></pre>
On making a request to the home page, "index.ntl" will be rendered as HTML.
