What does nodejs template do?

Node.js templates are an important part of creating web applications, making it easier for developers to manage and render HTML, CSS, and JavaScript. The purpose of Node.js templates is to separate data from the application's processing logic and separate it from the interface. This separation allows developers to better manage the code and make changes and maintenance easier. In this article, we'll take a closer look at Node.js templates, explore its uses, and how to use it to build web applications.

What are Node.js templates?

Node.js templates can preprocess data in code before rendering it on a web application page. A Node.js template is usually a string containing HTML, CSS, and JavaScript code that are replaced by placeholders through specific symbols or syntax. Placeholders are composed of specific syntax markers, usually symbols such as curly braces, greater-than signs, and percent signs. At runtime, the placeholders are replaced with actual data, and the final page content is generated.

Why do you need Node.js templates?

In traditional web development, mixing your application's business logic with HTML and CSS can lead to a confusing mess of code. If an application requires modification or reorganization of HTML/CSS, the modifications may need to be made throughout the code base, which can lead to bugs and difficult-to-maintain code. Therefore, using a template engine can separate data and page code, making the code easier to expand and maintain.

Node.js Template Usage

There are many different options for Node.js’s template engine, each with its own unique syntax and functionality. Here are some of the most popular Node.js template engines and their usage.

1. EJS

EJS (Embedded JavaScript) is a JavaScript template engine that allows JavaScript code to be embedded in HTML code using JavaScript. This makes EJS particularly useful when dealing with an application's interface, as it can use JavaScript to integrate other functionality such as database queries, calculations, etc.

When using EJS, we can use JavaScript-like function calls to output HTML.

const ejs = require('ejs');
const template = `<h1><%= message %></h1>`;
const data = {message: 'Hello EJS'};
const html = ejs.render(template, data);
console.log(html);

In this example, we just replace some text data with variables defined in the template string.

2. Handlebars

Handlebars is a JavaScript template engine based on Mustache templates that can generate HTML fragments. In Handlebars, you can use the {{}} symbol and the # symbol to reference variables and control structures, such as if and for loops.

The following is a Handlebars template for building an article list.

<ul>
 {{ #each articles }}
  <li><a href="{{ url }}">{{ title }}</a></li>
 {{ /each }}
</ul>

In this example, use #each to correspond to each article in the articles array, and output the title and URL of the article.

3. Jade (now called Pug)

Jade (now called Pug) is a template engine similar to HAML. It is ideal for rapid development of web applications because it simplifies the syntax of HTML, making the code cleaner.

The following is a simple form page written in Pug.

form(action="/submit-form", method="post")
  label(for="id-email") Email:
  input(name="email", id="id-email", type="email", required)
  br
  label(for="id-password") Password:
  input(name="password", id="id-password", type="password", required)
  br
  button(type="submit") Submit

In this example, we can see how to use indentation to represent hierarchy.

Summary

Template engines are an important part of building web applications because they can easily manage and render HTML, CSS, and JavaScript. Using a template engine separates an application's logic from its interface, making the code easier to write and maintain. There are many different Node.js template engines to choose from, each with its own unique syntax and functionality, and developers can choose one of them based on their needs.

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