Exploring Eleventy with TypeScript

Eleventy, often referred to as 11ty, is a simple yet powerful static site generator. It’s known for its flexibility and ease of use, allowing developers to build websites using a variety of templating languages. On the other hand, TypeScript is a superset of JavaScript that adds static typing to the language, enhancing code reliability and maintainability. Combining Eleventy with TypeScript can significantly improve the development experience, especially for larger projects where code organization and type safety are crucial. In this blog post, we’ll dive into the fundamental concepts of using Eleventy with TypeScript, explore usage methods, common practices, and best practices.

Table of Contents

  1. Fundamental Concepts
  2. Usage Methods
  3. Common Practices
  4. Best Practices
  5. Conclusion
  6. References

Fundamental Concepts

Eleventy Basics

Eleventy is a static site generator that takes input files (such as Markdown, HTML, or JavaScript) and processes them into output files (usually HTML). It uses a concept of “templates” to define how the content should be rendered. Eleventy supports multiple templating languages out of the box, including Liquid, Nunjucks, and Handlebars.

TypeScript Basics

TypeScript is a programming language that builds on JavaScript by adding static types. It allows developers to catch errors early in the development process and provides better code documentation. TypeScript code needs to be transpiled into JavaScript before it can be run in a browser or on a server.

Combining Eleventy and TypeScript

When using Eleventy with TypeScript, we can use TypeScript to write custom filters, shortcodes, and other Eleventy plugins. This allows us to take advantage of TypeScript’s type checking and code organization features while building our static sites.

Usage Methods

Setting up a new Eleventy project with TypeScript

  1. Create a new project directory:
mkdir eleventy-typescript-project
cd eleventy-typescript-project
  1. Initialize a new npm project:
npm init -y
  1. Install Eleventy and TypeScript:
npm install @11ty/eleventy typescript --save-dev
  1. Configure TypeScript: Create a tsconfig.json file in the root of your project with the following content:
{
  "compilerOptions": {
    "target": "ES6",
    "module": "commonjs",
    "outDir": "./dist",
    "rootDir": "./src",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true
  }
}
  1. Create an Eleventy configuration file in TypeScript: Create a eleventy.config.ts file in the root of your project. Here’s a basic example:
import { EleventyConfig } from "@11ty/eleventy";

export default (eleventyConfig: EleventyConfig) => {
  // Add a custom filter
  eleventyConfig.addFilter("uppercase", (str: string) => {
    return str.toUpperCase();
  });

  return {
    dir: {
      input: "src",
      output: "dist"
    }
  };
};
  1. Create a build script in package.json:
{
  "scripts": {
    "build": "npx tsc && npx eleventy",
    "serve": "npx tsc && npx eleventy --serve"
  }
}

Using TypeScript in Eleventy templates

You can use TypeScript functions in your Eleventy templates by registering them as filters or shortcodes. For example, in a Nunjucks template, you can use the uppercase filter we defined earlier:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Eleventy with TypeScript</title>
</head>
<body>
  <p>{{ "hello world" | uppercase }}</p>
</body>
</html>

Common Practices

Organizing TypeScript code

  • Separate concerns: Keep your filters, shortcodes, and other plugins in separate files. For example, you can create a filters.ts file to store all your custom filters:
export const uppercase = (str: string) => {
  return str.toUpperCase();
};

Then import and register them in your eleventy.config.ts file:

import { EleventyConfig } from "@11ty/eleventy";
import { uppercase } from "./filters";

export default (eleventyConfig: EleventyConfig) => {
  eleventyConfig.addFilter("uppercase", uppercase);

  return {
    dir: {
      input: "src",
      output: "dist"
    }
  };
};
  • Use namespaces or modules: Group related functions and types together using namespaces or modules to improve code organization.

Error handling

  • Type checking: Use TypeScript’s type checking to catch errors early in the development process. Make sure all your function parameters and return values have appropriate types.
  • Try-catch blocks: Use try-catch blocks when making asynchronous calls or performing operations that can throw errors.

Best Practices

Performance optimization

  • Minimize transpilation time: Keep your TypeScript codebase small and modular to reduce the time it takes to transpile your code.
  • Use caching: Eleventy has built-in caching mechanisms. Make sure to configure them properly to avoid unnecessary reprocessing of files.

Testing

  • Unit testing: Write unit tests for your TypeScript functions using a testing framework like Jest. This helps ensure the correctness of your code and makes it easier to refactor.
  • Integration testing: Test your Eleventy templates and plugins in an integration testing environment to make sure they work together as expected.

Conclusion

Combining Eleventy with TypeScript can bring significant benefits to your static site development workflow. By using TypeScript’s type checking and code organization features, you can write more reliable and maintainable code. In this blog post, we’ve covered the fundamental concepts, usage methods, common practices, and best practices of using Eleventy with TypeScript. We hope this guide helps you get started and make the most out of this powerful combination.

References