Templating is crucial for dynamic web application development. It allows developers to efficiently render data into reusable UI components. While numerous templating libraries exist, Underscore.js as a template engine provides a lightweight and flexible solution, especially for projects already leveraging Underscore’s utility functions. This article will guide you through the process of using Underscore.js templates, explaining how to define, compile, and render templates with real-world examples. We’ll explore the syntax, available options, and best practices, empowering you to create efficient and maintainable web applications. Underscore’s simplicity and small footprint make it an excellent choice for projects where performance and ease of use are paramount. This guide will also help you understand how Underscore.js compares to other templating engines and when it might be the most suitable option for your needs.

Understanding Underscore.js Templates

Underscore.js is a JavaScript library that provides a collection of utility functions for common programming tasks. One of its features is a templating engine that allows you to create dynamic HTML content. Underscore.js as a template engine is known for its simplicity and flexibility. It uses a micro-templating syntax that is easy to learn and use. The template engine works by compiling a template string into a JavaScript function, which can then be executed with a data object to produce the final HTML output. This approach allows for efficient rendering and easy integration with other JavaScript libraries and frameworks. According to the official Underscore.js documentation, its templating function is inspired by John Resig’s micro-templating implementation. Learn more about Underscore.js here.

The core of Underscore.js templating is the _.template() function. This function takes a template string as input and returns a compiled template function. The template string can contain JavaScript code snippets enclosed in special delimiters. By default, these delimiters are <%= %> for evaluating JavaScript expressions, <%- %> for escaping HTML, and <% %> for executing JavaScript code. However, these delimiters can be customized to avoid conflicts with other templating systems or to match your preferred coding style. The compiled template function can then be called with a data object, which will be used to populate the template with dynamic values.

Using Underscore.js templates can significantly improve the maintainability and readability of your code. By separating the presentation logic from the application logic, you can create cleaner and more organized codebases. Templates also promote code reuse, as the same template can be used to render different data sets. Furthermore, the simple syntax of Underscore.js templates makes it easy for developers to understand and modify them, even if they are not familiar with the library. This is particularly useful in large teams where multiple developers may be working on the same project.

Setting Up and Using Underscore.js for Templating

Before you can start using Underscore.js as a template engine, you need to include the Underscore.js library in your project. You can do this by downloading the library from the Underscore.js website or by using a package manager like npm or yarn. Once you have included the library, you can access the _.template() function to compile your templates. The following steps will guide you through the process of setting up and using Underscore.js for templating. According to a Stack Overflow survey, Underscore.js, while not as popular as React or Angular, is still used by a significant number of developers for utility functions, including templating. Check out the Stack Overflow Developer Survey 2023.

1. Include Underscore.js: Add the Underscore.js library to your HTML file using a <script> tag. You can either download the library and include it locally or use a CDN link.
2. Define Your Template: Create a template string containing the HTML structure and JavaScript code snippets for dynamic data. Use the delimiters <%= %>, <%- %>, and <% %> to embed JavaScript code.
3. Compile the Template: Use the _.template() function to compile the template string into a JavaScript function.
4. Render the Template: Call the compiled template function with a data object to produce the final HTML output.
5. Append to the DOM: Insert the rendered HTML into the desired element in your HTML document.

Here’s an example of how to use Underscore.js templates:

<script src="underscore-min.js"></script> <div id="container"></div> <script> var templateString = '<h2><%- title %></h2><p><%= description %></p>'; var compiledTemplate = _.template(templateString); var data = { title: 'My Article', description: 'This is a sample article rendered using Underscore.js templates.' }; var renderedHTML = compiledTemplate(data); document.getElementById('container').innerHTML = renderedHTML; </script> 

This code snippet demonstrates how to include Underscore.js, define a template string, compile it using _.template(), pass data to the compiled template, and then insert the rendered HTML into a div element with the id “container”. This simple example illustrates the basic steps involved in using Underscore.js templates to dynamically generate HTML content.

Advanced Templating Techniques

While the basic usage of Underscore.js as a template engine is straightforward, there are several advanced techniques that can help you create more complex and efficient templates. One such technique is using template settings to customize the delimiters and other options. Another technique is using helper functions to perform common tasks within your templates. These helper functions can simplify your templates and make them more readable. Additionally, you can use conditional statements and loops within your templates to generate dynamic content based on the data you provide. Click here to learn more about templating.

Template settings allow you to customize the delimiters used to embed JavaScript code in your templates. This can be useful if you are working with other templating systems that use the same delimiters, or if you simply prefer a different syntax. You can customize the interpolate, escape, and evaluate delimiters using the _.templateSettings object. For example, you can change the interpolate delimiter to {{ }} by setting _.templateSettings.interpolate = /\{\{(.+?)\}\}/g;. This will allow you to use {{ title }} to embed the value of the title variable in your template.

Helper functions can be used to perform common tasks within your templates, such as formatting dates, converting strings to uppercase, or generating HTML snippets. You can define these helper functions in your JavaScript code and then pass them to the template as part of the data object. For example, you can define a helper function called formatDate that takes a date object as input and returns a formatted date string. You can then use this function in your template by calling <%= formatDate(date) %>. Using helper functions can significantly simplify your templates and make them more readable.

Here are some key points to remember when using advanced templating techniques:

• Customize delimiters to avoid conflicts and match your preferred style.
• Use helper functions to simplify templates and promote code reuse.
• Leverage conditional statements and loops for dynamic content generation.

Best Practices and Common Pitfalls

When working with Underscore.js as a template engine, it’s important to follow best practices to ensure your templates are efficient, maintainable, and secure. One common pitfall is injecting unsanitized user input into your templates, which can lead to cross-site scripting (XSS) vulnerabilities. Another pitfall is overusing JavaScript code within your templates, which can make them difficult to read and maintain. It’s also important to optimize your templates for performance, especially if you are rendering large amounts of data. According to OWASP, proper input validation and output encoding are crucial for preventing XSS attacks. Read more about XSS prevention on OWASP.

To prevent XSS vulnerabilities, always escape user input before injecting it into your templates. You can use the <%- %> delimiter to escape HTML entities, which will prevent malicious code from being executed in the user’s browser. It’s also important to validate user input to ensure it conforms to the expected format and does not contain any potentially harmful characters. By following these security best practices, you can protect your web application from XSS attacks.

To improve the readability and maintainability of your templates, avoid overusing JavaScript code. Instead, try to move complex logic into helper functions that can be called from within your templates. This will make your templates more concise and easier to understand. It’s also a good idea to use comments to document your templates and explain the purpose of each section. By following these coding best practices, you can create templates that are easy to maintain and modify.

Featured Snippet Optimized: To optimize your templates for performance, minimize the amount of JavaScript code that needs to be executed during rendering. Use caching to store the results of expensive computations and avoid unnecessary DOM manipulations. Consider using template pre-compilation to compile your templates ahead of time, which can improve rendering performance. By following these performance optimization tips, you can ensure your templates render quickly and efficiently.

What is Underscore.js?

Underscore.js is a JavaScript library that provides a collection of utility functions for common programming tasks, including templating, array manipulation, and object manipulation.

How do I include Underscore.js in my project?

You can include Underscore.js in your project by downloading the library from the Underscore.js website or by using a package manager like npm or yarn.

How do I define a template in Underscore.js?

You can define a template in Underscore.js by creating a template string containing the HTML structure and JavaScript code snippets for dynamic data.

How do I compile a template in Underscore.js?

You can compile a template in Underscore.js using the `_.template()` function, which takes a template string as input and returns a compiled template function.

How do I render a template in Underscore.js?

You can render a template in Underscore.js by calling the compiled template function with a data object, which will be used to populate the template with dynamic values.

Question & Answer :
I’m trying to learn about new usages of javascript as a serverside language and as a functional language. Few days ago I heard about node.js and express framework. Then I saw about underscore.js as a set of utility functions. I saw this question on stackoverflow . It says we can use underscore.js as a template engine. anybody know good tutorials about how to use underscore.js for templating, especially for biginners who have less experience with advanced javascript. Thanks

Everything you need to know about underscore template is here. Only 3 things to keep in mind:

1. <% %> - to execute some code
2. <%= %> - to print some value in template
3. <%- %> - to print some values HTML escaped

That’s all about it.

Simple example:

var tpl = _.template("<h1>Some text: <%= foo %></h1>"); 

then tpl({foo: "blahblah"}) would be rendered to the string <h1>Some text: blahblah</h1>