JanjaTemplates that compile to JavaScript

A simple, fast, lightweight and extensible template engine for Node.js and browsers.

Small language, fully specified

Output, conditions, loops, macros, layouts and filters. Every rule of the specification is backed by a conformance suite.

Read the specification

Fast

Templates compile to JavaScript functions, cached per renderer or pre-compiled at build time into plain ES modules.

Benchmarks

Safe by default

Output is HTML-escaped, and expressions cannot reach JavaScript globals or object internals.

What is and is not covered

Errors that point at the template

Errors throw by default and show the offending line. A lenient mode and a validator are there when you need them.

Error handling

Async and streaming

Async filters and loaders, and renderStream() to send the start of a page while the rest still renders.

Streaming

Tooling included

A CLI, a formatter, a language server, a VS Code extension, a Vite plugin, and adapters for Express, Koa and Fastify.

Ecosystem

Try it

Edit the template or its data; it renders in your browser.

janja

<h1>Hello, {{= name | capitalize }}!</h1>
{{ for task of tasks }}
  <p>{{= loop.index + 1 }}. {{= task.title }}{{= " ✓" if task.done }}</p>
{{ else }}
  <p>Nothing to do.</p>
{{ endfor }}

Data (JSON)

{
  "name": "world",
  "tasks": [
    { "title": "Write a template", "done": true },
    { "title": "Render it", "done": false }
  ]
}

OutputOpen in playground

bash

npm install janja