# Nunjucks — Rich Templating Engine for JavaScript by Mozilla

> A powerful templating engine for JavaScript inspired by Jinja2, featuring template inheritance, macros, asynchronous rendering, and auto-escaping for secure output.

## Install

Save as a script file and run:

# Nunjucks — Rich Templating Engine for JavaScript by Mozilla

## Quick Use
```bash
npm install nunjucks
```
```js
const nunjucks = require('nunjucks');
nunjucks.configure('views', {autoescape: true});
const result = nunjucks.render('index.html', {title: 'Home'});
console.log(result);
```

## Introduction
Nunjucks is a full-featured templating engine for JavaScript, created by Mozilla and inspired by Python's Jinja2. It supports template inheritance, macros, filters, and async rendering, making it suitable for both server-side HTML generation and browser-side template rendering.

## What Nunjucks Does
- Renders templates with variables, loops, conditionals, and filters
- Supports template inheritance with block overrides for layout reuse
- Provides macros for reusable template components with parameters
- Handles asynchronous data sources through async filters and extensions
- Auto-escapes output by default to prevent cross-site scripting

## Architecture Overview
Nunjucks compiles template strings into an intermediate AST, then generates optimized JavaScript render functions. A configurable loader system resolves template names from the filesystem (Node.js) or precompiled bundles (browser). The runtime maintains a context stack for variable scoping and supports synchronous and asynchronous rendering modes through the same template API.

## Self-Hosting & Configuration
- Install via npm for Node.js or precompile templates for the browser
- Call nunjucks.configure() with a template directory and options like autoescape
- Use nunjucks.render(name, context) for synchronous or callback-based rendering
- Precompile templates with the nunjucks-precompile CLI for client-side use
- Register custom filters and extensions for domain-specific template logic

## Key Features
- Jinja2-compatible syntax familiar to Python developers
- Template inheritance with extendable blocks for consistent layouts
- Macros and imports for reusable template components across files
- Async-capable rendering for templates that need to fetch data
- Built-in auto-escaping with safe filter for trusted content

## Comparison with Similar Tools
- **Handlebars** — simpler logic-less syntax with helpers; no template inheritance or macros
- **EJS** — embeds raw JavaScript in templates; more flexible but less structured
- **Mustache.js** — minimal logic-less templates; no filters, inheritance, or async support
- **Pug** — indentation-based HTML syntax; different authoring style and tighter HTML coupling

## FAQ
**Q: Can Nunjucks run in the browser?**
A: Yes, precompile your templates and include the slim runtime bundle for client-side rendering.

**Q: Is Nunjucks compatible with Jinja2 templates?**
A: Mostly yes. Core syntax is the same, but some Python-specific filters and behaviors differ.

**Q: Does Nunjucks support streaming output?**
A: No, it renders the full output as a string. For streaming, consider rendering in chunks manually.

**Q: How do I add custom filters?**
A: Call env.addFilter(name, function) on a configured environment to register filters globally.

## Sources
- https://github.com/mozilla/nunjucks
- https://mozilla.github.io/nunjucks/

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Source: https://tokrepo.com/en/workflows/asset-4259c2de
Author: Script Depot