EJS

EJS
Name	EJS
Developer	Embedded JavaScript (community)
Initial release	2009
Latest release	3.x
Programming language	JavaScript
Genre	Templating engine
License	MIT License

EJS EJS is a templating engine for embedding JavaScript code into text documents, primarily used to generate HTML from templates. It enables separation of presentation from application logic in web applications developed with Node.js, Express (web framework), Koa (web framework), Hapi (software), and other JavaScript-based stacks. EJS templates intermix static markup with dynamic expressions and control structures drawn from the ECMAScript language, facilitating server-side rendering for projects associated with ecosystems such as npm, Yarn, GitHub, and deployment targets like Heroku, Vercel, and AWS Elastic Beanstalk.

Overview

EJS operates by compiling template files containing plain text and embedded tags into JavaScript functions that produce output strings when executed. It integrates with view engines used by Express (web framework), Sails.js, AdonisJS, and LoopBack to render responses for routes defined in applications built with frameworks such as Meteor (web framework), Next.js, and Nuxt.js (when used with server-side rendering shims). Common use cases include rendering dynamic pages for projects served by Apache HTTP Server or Nginx reverse proxies, crafting email templates for services like SendGrid, and generating static sites with tools inspired by Jekyll and Hugo.

History

EJS emerged in the late 2000s amid efforts to bring lightweight, logic-capable templating to the increasing popularity of Node.js and asynchronous JavaScript servers. Influences include earlier engines such as ERB used in Ruby on Rails and templating concepts from PHP, ASP.NET, and JSP. Over time, EJS evolved alongside package management trends driven by npm and version control workflows centered on Git, accumulating community contributions and forks on GitHub and integrations tested in continuous integration setups like Travis CI and CircleCI. Significant ecosystem milestones coincide with major releases of Node.js (e.g., Node 0.10, 4.x, 6.x, 8.x, 12.x) and shifts toward modern ECMAScript standards promoted by TC39.

Syntax and Features

EJS templates combine static markup with embedded JavaScript delimited by tags. Common tags include <% %> for scriptlets, <%= %> for escaped output, and <%- %> for unescaped output; these reflect conventions similar to ERB and Smarty used with projects like Django and Laravel when compared across ecosystems. Features include layout partials compatible with view engines in Express (web framework), includes for modular templates used in Handlebars and Mustache workflows, custom delimiter configuration reminiscent of Lodash templating, and support for filters and helpers that parallel patterns found in Underscore.js and Lo-Dash.

EJS exposes options to control caching, filename resolution, and compile-time behavior—settings often adjusted in deployment scenarios on Google Cloud Platform, Microsoft Azure, or DigitalOcean. Its approach to escaping and raw output requires developers to be familiar with OWASP recommendations for preventing injection vulnerabilities and XSS responsibilities emphasized in guidance from CWE and standards discussed by W3C.

Usage and Integration

Developers typically install EJS via npm or Yarn and configure it as the view engine in Express (web framework) applications using app.set('view engine', ...). It integrates with middleware ecosystems including Passport (authentication), multer (multipart), and body-parser to render responses after authentication flows or form submissions tied to patterns from OAuth and OpenID Connect implementations. In full-stack projects that combine client-side frameworks like React (web framework), Vue.js, or Angular with server-rendered templates, EJS can be used for initial HTML shell generation while client bundles are served from CDNs such as Cloudflare or Fastly.

EJS also appears in static site generation pipelines and build tools including Gulp, Grunt, and Webpack (through appropriate loaders), enabling template-based asset generation for sites deployed to Netlify or archived with GitHub Pages. Continuous delivery pipelines leveraging Jenkins, GitLab CI, or Azure DevOps commonly include steps that render templates into environment-specific files.

Performance and Security Considerations

Performance of EJS depends on compile-time caching, template complexity, and underlying V8 (JavaScript engine) optimizations present in the Node.js runtime. For high-throughput services behind load balancers such as HAProxy or AWS ELB, precompiling templates and enabling caching reduces CPU overhead, while asynchronous I/O patterns favored by Node.js should be maintained in request handlers. Security considerations focus on proper escaping to prevent cross-site scripting; adherence to guidance from OWASP and awareness of common weaknesses cataloged by CWE are critical. When rendering untrusted data, developers should prefer escaped output tags and sanitize inputs with libraries like DOMPurify or server-side validators referenced in specifications by IETF for internet standards.

Alternatives and Comparison

EJS is one among several templating options in the JavaScript ecosystem. Direct competitors include Handlebars (templating), Mustache, Pug (template engine), Nunjucks, and Dust.js; each offers trade-offs in syntax, logic support, and performance comparable to templating in Ruby on Rails or ASP.NET MVC. Client-side alternatives like React (web framework)'s JSX and Vue.js templates shift rendering responsibilities, while server-rendered frameworks such as Next.js and Nuxt.js provide integrated solutions that may obviate standalone templating engines. Choice among these depends on project requirements, developer familiarity, and integration needs with platforms like Heroku, Vercel, or enterprise environments leveraging Docker and Kubernetes.

Category:Template engines