Templating Engines

Templating engines are tools that help developers build dynamic HTML pages. They allow you to inject data into templates and generate HTML content dynamically. Express.js supports various templating engines, making it easier to create server-rendered views. In this chapter, we'll explore different templating engines, how to integrate them with Express.js, and best practices for using them.

Bonus : Practical example in the end💡

Templating Engine?

A templating engine allows you to create HTML templates with embedded code. This code is replaced with data when the template is rendered, allowing for dynamic content generation. Templating engines help separate the presentation layer from the business logic, making your code cleaner and easier to maintain.

Popular Templating Engines

Several templating engines are commonly used with Express.js:

  • EJS (Embedded JavaScript): Simple and powerful, with JavaScript-like syntax.
  • Pug (formerly Jade): Minimalist syntax and indentation-based, making it very concise.
  • Handlebars: Logic-less templates with a focus on simplicity and readability.

Setting Up Templating Engines in Express.js

To use a templating engine in Express.js, you need to set the view engine and configure the views directory.

Example: Basic Setup

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

// Set the view engine
app.set('view engine', 'ejs');

// Set the views directory
app.set('views', './views');

// Define a route
app.get('/', (req, res) => {
    res.render('index', { title: 'Welcome', message: 'Hello, World!' });
});

// Start the server
app.listen(3000, () => {
    console.log('Server is running on port 3000');
});

In this example, we set EJS as the view engine and define the directory where our views will be stored.

Using EJS (Embedded JavaScript)

EJS is a simple templating engine that lets you generate HTML with plain JavaScript.

				
					npm install ejs

Creating Views

Create a directory named views and add an index.ejs file:

				
					
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title><%= title %></title>
</head>
<body>
    <h1><%= message %></h1> <script data-no-optimize="1">window.lazyLoadOptions=Object.assign({},{threshold:300},window.lazyLoadOptions||{});!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?module.exports=e():"function"==typeof define&&define.amd?define(e):(t="undefined"!=typeof globalThis?globalThis:t||self).LazyLoad=e()}(this,function(){"use strict";function e(){return(e=Object.assign||function(t){for(var e=1;e<arguments.length;e++){var n,a=arguments[e];for(n in a)Object.prototype.hasOwnProperty.call(a,n)&&(t[n]=a[n])}return t}).apply(this,arguments)}function o(t){return e({},at,t)}function l(t,e){return t.getAttribute(gt+e)}function c(t){return l(t,vt)}function s(t,e){return function(t,e,n){e=gt+e;null!==n?t.setAttribute(e,n):t.removeAttribute(e)}(t,vt,e)}function i(t){return s(t,null),0}function r(t){return null===c(t)}function u(t){return c(t)===_t}function d(t,e,n,a){t&&(void 0===a?void 0===n?t(e):t(e,n):t(e,n,a))}function f(t,e){et?t.classList.add(e):t.className+=(t.className?" 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</html>

Rendering Views

Modify the route in server.js:

				
					app.get('/', (req, res) => {
    res.render('index', { title: 'Welcome', message: 'Hello, World!' });
});

Explanation:

  • <%= title %> and <%= message %> are placeholders that will be replaced with the actual values passed to the res.render method.

Output:

Navigating to http://localhost:3000/ will display a page with “Welcome” as the title and “Hello, World!” as the message.

Using Pug (formerly Jade)

Setting Up Pug

Pug is a templating engine with a minimalist syntax, focusing on indentation.

				
					npm install pug

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

app.set('view engine', 'pug');
app.set('views', './views');

app.get('/', (req, res) => {
    res.render('index', { title: 'Welcome', message: 'Hello, World!' });
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});

Creating Views

Create an index.pug file:

				
					// views/index.pug
doctype html
html(lang="en")
  head
    meta(charset="UTF-8")
    meta(name="viewport" content="width=device-width, initial-scale=1.0")
    title= title
  body
    h1= message

Explanation:

  • Pug uses indentation to define HTML structure, making it concise and readable.

Output:

Navigating to http://localhost:3000/ will display a page with “Welcome” as the title and “Hello, World!” as the message.

Using Handlebars

Setting Up Handlebars

Handlebars is a logic-less templating engine, known for its simplicity and readability.

				
					npm install express-handlebars

				
			
				
					const express = require('express');
const exphbs = require('express-handlebars');
const app = express();

app.engine('handlebars', exphbs());
app.set('view engine', 'handlebars');
app.set('views', './views');

app.get('/', (req, res) => {
    res.render('index', { title: 'Welcome', message: 'Hello, World!' });
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});

Creating Views

Create an index.handlebars file:

				
					
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>{{title}}</title>
</head>
<body>
    <h1>{{message}}</h1> <script data-no-optimize="1">window.lazyLoadOptions=Object.assign({},{threshold:300},window.lazyLoadOptions||{});!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?module.exports=e():"function"==typeof define&&define.amd?define(e):(t="undefined"!=typeof globalThis?globalThis:t||self).LazyLoad=e()}(this,function(){"use strict";function e(){return(e=Object.assign||function(t){for(var e=1;e<arguments.length;e++){var n,a=arguments[e];for(n in a)Object.prototype.hasOwnProperty.call(a,n)&&(t[n]=a[n])}return t}).apply(this,arguments)}function o(t){return e({},at,t)}function l(t,e){return t.getAttribute(gt+e)}function c(t){return l(t,vt)}function s(t,e){return function(t,e,n){e=gt+e;null!==n?t.setAttribute(e,n):t.removeAttribute(e)}(t,vt,e)}function i(t){return s(t,null),0}function r(t){return null===c(t)}function u(t){return c(t)===_t}function d(t,e,n,a){t&&(void 0===a?void 0===n?t(e):t(e,n):t(e,n,a))}function f(t,e){et?t.classList.add(e):t.className+=(t.className?" 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</html>

Explanation:

  • {{title}} and {{message}} are placeholders that will be replaced with the actual values passed to the res.render method.

Output:

Navigating to http://localhost:3000/ will display a page with “Welcome” as the title and “Hello, World!” as the message.

Advanced Usage

Templating engines offer more advanced features like partials, layouts, and helpers.

Partials in EJS

Partials allow you to reuse pieces of templates.

Example:

Create a header.ejs partial:

				
					
<header>
    <h1><%= title %></h1>
</header>

Include the partial in index.ejs:

				
					
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title><%= title %></title>
</head>
<body>
    <%- include('partials/header') %>
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d=document.createElement("script");d.addEventListener("load",e),d.addEventListener("error",e),t.getAttributeNames().forEach(e=>{"type"!=e&&d.setAttribute("data-src"==e?"src":e,t.getAttribute(e))});let a=!(d.type="text/javascript");!d.src&&t.textContent&&(d.src=litespeed_inline2src(t.textContent),a=!0),t.after(d),t.remove(),a&&e()}function litespeed_inline2src(t){try{var d=urlCreator.createObjectURL(new Blob([t.replace(/^(?:<!--)?(.*?)(?:-->)?$/gm,"$1")],{type:"text/javascript"}))}catch(e){d="data:text/javascript;base64,"+btoa(t.replace(/^(?:<!--)?(.*?)(?:-->)?$/gm,"$1"))}return d}</script><script data-optimized="1" type="litespeed/javascript" data-src="https://diginode.in/wp-content/litespeed/js/5ad5da7e80e1ecf64f3d75c5dab7ddb4.js?ver=c45bf"></script></body>
</html>

Explanation:

  • <%- include('partials/header') %> includes the header.ejs partial in the main template.

Layouts in Handlebars

Layouts help you define a common structure for your templates.

Example:

Create a main.handlebars layout:

				
					
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>{{title}}</title>
</head>
<body>
    {{{body}}} <script data-no-optimize="1">window.lazyLoadOptions=Object.assign({},{threshold:300},window.lazyLoadOptions||{});!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?module.exports=e():"function"==typeof define&&define.amd?define(e):(t="undefined"!=typeof globalThis?globalThis:t||self).LazyLoad=e()}(this,function(){"use strict";function e(){return(e=Object.assign||function(t){for(var e=1;e<arguments.length;e++){var n,a=arguments[e];for(n in a)Object.prototype.hasOwnProperty.call(a,n)&&(t[n]=a[n])}return t}).apply(this,arguments)}function o(t){return e({},at,t)}function l(t,e){return t.getAttribute(gt+e)}function c(t){return l(t,vt)}function s(t,e){return function(t,e,n){e=gt+e;null!==n?t.setAttribute(e,n):t.removeAttribute(e)}(t,vt,e)}function i(t){return s(t,null),0}function r(t){return null===c(t)}function u(t){return c(t)===_t}function d(t,e,n,a){t&&(void 0===a?void 0===n?t(e):t(e,n):t(e,n,a))}function f(t,e){et?t.classList.add(e):t.className+=(t.className?" 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d=document.createElement("script");d.addEventListener("load",e),d.addEventListener("error",e),t.getAttributeNames().forEach(e=>{"type"!=e&&d.setAttribute("data-src"==e?"src":e,t.getAttribute(e))});let a=!(d.type="text/javascript");!d.src&&t.textContent&&(d.src=litespeed_inline2src(t.textContent),a=!0),t.after(d),t.remove(),a&&e()}function litespeed_inline2src(t){try{var d=urlCreator.createObjectURL(new Blob([t.replace(/^(?:<!--)?(.*?)(?:-->)?$/gm,"$1")],{type:"text/javascript"}))}catch(e){d="data:text/javascript;base64,"+btoa(t.replace(/^(?:<!--)?(.*?)(?:-->)?$/gm,"$1"))}return d}</script><script data-optimized="1" type="litespeed/javascript" data-src="https://diginode.in/wp-content/litespeed/js/5ad5da7e80e1ecf64f3d75c5dab7ddb4.js?ver=c45bf"></script></body>
</html>

Use the layout in index.handlebars:

				
					
<p>{{message}}</p>

Modify the route in server.js:

				
					app.get('/', (req, res) => {
    res.render('index', { layout: 'main', title: 'Welcome', message: 'Hello, World!' });
});

Explanation:

  • The main.handlebars layout provides a common structure, and the {{{body}}} placeholder is replaced with the content of the index.handlebars template.
Templating Engine

Best Practices

  • Separate Logic from Presentation: Keep your business logic separate from your presentation layer to maintain clean and maintainable code.

  • Use Partials and Layouts: Reuse common template sections using partials and layouts to avoid duplication.

  • Sanitize User Input: Prevent XSS attacks by properly sanitizing user input in your templates.

  • Cache Templates: Improve performance by caching templates in production environments.

Real-World Example: Building a Blog Application

Let’s build a simple blog application that uses EJS for templating.

Project Structure

				
					blog-app/
├── node_modules/
├── views/
│   ├── layouts/
│   │   └── main.ejs
│   ├── partials/
│   │   └── header.ejs
│   ├── index.ejs
│   └── post.ejs
├── public/
│   └── styles.css
├── server.js
└── package.json

Installation

				
					npm install express ejs

Server Setup

server.js:

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

app.set('view engine', 'ejs');
app.set('views', './views');

app.use(express.static('public'));

const posts = [
    { title: 'First Post', content: 'This is the first post.' },
    { title: 'Second Post', content: 'This is the second post.' }
];

app.get('/', (req, res) => {
    res.render('index', { posts });
});

app.get('/post/:id', (req, res) => {
    const post = posts[req.params.id];
    if (post) {
        res.render('post', { post });
    } else {
        res.status(404).send('Post not found');
    }
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});

Views

views/layouts/main.ejs:

				
					<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title><%= title %></title>
    <link rel="stylesheet" href="/styles.css">
</head>
<body>
    <%- include('../partials/header') %>
    <div class="content">
        <%- body %>
    </div> <script data-no-optimize="1">window.lazyLoadOptions=Object.assign({},{threshold:300},window.lazyLoadOptions||{});!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?module.exports=e():"function"==typeof define&&define.amd?define(e):(t="undefined"!=typeof globalThis?globalThis:t||self).LazyLoad=e()}(this,function(){"use strict";function e(){return(e=Object.assign||function(t){for(var e=1;e<arguments.length;e++){var n,a=arguments[e];for(n in a)Object.prototype.hasOwnProperty.call(a,n)&&(t[n]=a[n])}return t}).apply(this,arguments)}function o(t){return e({},at,t)}function l(t,e){return t.getAttribute(gt+e)}function c(t){return l(t,vt)}function s(t,e){return function(t,e,n){e=gt+e;null!==n?t.setAttribute(e,n):t.removeAttribute(e)}(t,vt,e)}function i(t){return s(t,null),0}function r(t){return null===c(t)}function u(t){return c(t)===_t}function d(t,e,n,a){t&&(void 0===a?void 0===n?t(e):t(e,n):t(e,n,a))}function f(t,e){et?t.classList.add(e):t.className+=(t.className?" 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</html>

views/partials/header.ejs:

				
					<header>
    <h1>My Blog</h1>
    <nav>
        <a href="/">Home</a>
    </nav>
</header>

views/index.ejs:

				
					<% posts.forEach((post, index) => { %>
    <article>
        <h2><a href="/post/<%= index %>"><%= post.title %></a></h2>
        <p><%= post.content %></p>
    </article>
<% }) %>

views/post.ejs:

				
					<article>
    <h2><%= post.title %></h2>
    <p><%= post.content %></p>
    <a href="/">Back to Home</a>
</article>

public/styles.css:

				
					body {
    font-family: Arial, sans-serif;
    padding: 20px;
}

header {
    margin-bottom: 20px;
}

header h1 {
    margin: 0;
}

nav a {
    margin-right: 10px;
}

.content {
    max-width: 800px;
    margin: 0 auto;
}

article {
    margin-bottom: 20px;
}

article h2 {
    margin: 0 0 10px;
}

Explanation:

  • The server.js file sets up the server, defines routes, and renders views using EJS.
  • The main.ejs layout provides a common structure for all pages.
  • The header.ejs partial contains the header section of the pages.
  • The index.ejs template lists all blog posts.
  • The post.ejs template displays a single blog post.

Output:

  • Navigating to http://localhost:3000/ displays a list of blog posts.
  • Clicking on a post title navigates to the post’s page, displaying the post content.

Templating engines are a powerful tool for creating dynamic web pages in Express.js. By using templating engines like EJS, Pug, and Handlebars, you can separate your presentation layer from your business logic, making your code cleaner and more maintainable. This chapter covered the basics and advanced usage of templating engines, providing practical examples and best practices. By mastering templating engines, you can build robust and dynamic web applications with Express.js.Happy coding !❤️

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