What are template engines in Express, and why are they used?

A Template Engine simplifies the use of static templates with minimal code. During runtime on the client side, variables in the template are replaced with actual values. These engines help developers create templates for web pages, written in a markup language with placeholders for dynamic content. When rendered, these placeholders are substituted with real data, producing a dynamic document.

We will learn about the following template engines and why they are used:

EJS:

EJS, or Embedded JavaScript Templating, is a templating engine utilized in Node.js. This engine assists in the creation of HTML templates with minimal code, allowing the injection of data into the template on the client side to generate the final HTML output. EJS serves as a straightforward templating language, utilizing plain JavaScript to generate HTML markup. Additionally, it facilitates the embedding of JavaScript into HTML pages. To initiate the use of EJS as a templating engine, installation is required via the provided command.

npm install ejs --save

Pug:

Pug serves as a template engine designed for both Node.js and browsers, facilitating the dynamic rendering of reusable content. During the compilation phase, Pug translates our template code into HTML. Similar to JavaScript, Pug allows the use of variables, which are later substituted with real values during runtime. The template engine then transforms the template into an HTML file, ready to be rendered on the client side.

Pug boasts numerous robust features, including conditions, loops, includes, and mixins, enabling the dynamic rendering of HTML code based on user input or referenced data. With native support for JavaScript, Pug allows the integration of JavaScript expressions to format HTML code. This approach empowers the reuse of static web pages by incorporating dynamic data seamlessly.

npm install express pug

Mustache:

Mustache stands out as a logicless template engine, serving as a valuable tool for generating dynamic content such as HTML and configuration files. The term “logicless” indicates its absence of structured flow elements like if-else statements, for loops, or while loops. Instead, Mustache employs tag names enclosed within double curly braces {{ }}, earning them the name “Mustache templates” due to their resemblance to a mustache.

To utilize Mustache, a model object is necessary, containing the data to be incorporated into the template. The simplicity of Mustache is particularly evident in its straightforward syntax, making it well-suited for various applications. Let’s explore its functionality within a Maven project.

Why Template Engines are Used?

A template engine empowers the utilization of static template files within an application. During runtime, variables in the template file are substituted with actual values, and the template is converted into an HTML file transmitted to the client. This method simplifies the design of HTML pages.

These engines come into play when swiftly constructing web applications with distinct components. Templates facilitate the quick rendering of server-side data essential for the application. Components like body, navigation, footer, dashboard, etc., can be efficiently managed.

The adoption of template engines enhances developer productivity, concurrently enhancing readability and maintainability.

Advantages of using Template Engines

• Template engines improves developer’s productivity. Improves readability and maintainability.
• Templates are easy to replicate; you can take them from one specific place instead of copying and pasting them every time;
• Template engines are used when you want to rapidly build web applications that are split into different components.
• emplates also enable fast rendering of the server-side data that needs to be passed to the application. For example, you might want to have components such as body, navigation, footer, dashboard, etc.
• Some templating engines can make pregeneration a bit easier and pre-compilation to make them faster

Example: Here is the basic example of ejs template engine:

Javascript

// Set express as Node.js web application
// server framework.
// To install express before using it as
// an application server by using
// "npm install express" command.
const express = require('express');
const app = express();

// Set EJS as templating engine
app.set('view engine', 'ejs');

const server = app.listen(4000,
    function () {
        console.log('listening to port 4000')
    });

Steps to run the program:

node index.js

Output: