Preprocessors Added in v3.0.0

Contents

Example: Drafts

The Preprocessor Configuration API allows you to intercept and modify the content in template files (not Layouts) before they’re processed and rendered by Eleventy.

eleventy.config.js

ESM CommonJS

export default function (eleventyConfig) {
  eleventyConfig.addPreprocessor("drafts", "njk,md,liquid", (data, content) => {
		if(data.draft) {
			// Ignore this file.
			return false;
		}

		// You can also modify the raw input of the template here too, be careful!
		return `${content}<!-- Template file: {{ page.inputPath }} -->`;

		// If you return nothing or `undefined`, no changes will be made to this template.
	});
};

module.exports = function (eleventyConfig) {
  eleventyConfig.addPreprocessor("drafts", "njk,md,liquid", (data, content) => {
		if(data.draft) {
			// Ignore this file.
			return false;
		}

		// You can also modify the raw input of the template here too, be careful!
		return `${content}<!-- Template file: {{ page.inputPath }} -->`;

		// If you return nothing or `undefined`, no changes will be made to this template.
	});
};

The first argument is an arbitrary name (String) used for error messaging.
The second argument can be:
- a String of comma separated file extensions
- an Array<String> of file extensions
Returning false will ignores the template in the same way as using eleventyConfig.ignores or .eleventyignore
Returning nothing or undefined has no effect (unlike Transforms)

Originally GitHub Issue #188.

Example: Drafts

Here’s an example that uses the Preprocessor API to implement a Drafts workflow.

Set draft: true anywhere in a file’s data cascade and that file will be only be built when using Eleventy in --serve or --watch modes. It will be excluded from full Eleventy builds.

You might imagine how this could be extended to add a publishing date feature too: to exclude content from builds before a specific date set in a post’s front matter (or elsewhere in the data cascade).

eleventy.config.js

ESM CommonJS

export default function (eleventyConfig) {
  eleventyConfig.addPreprocessor("drafts", "*", (data, content) => {
		if(data.draft && process.env.ELEVENTY_RUN_MODE === "build") {
			return false;
		}
	});
};

module.exports = function (eleventyConfig) {
  eleventyConfig.addPreprocessor("drafts", "*", (data, content) => {
		if(data.draft && process.env.ELEVENTY_RUN_MODE === "build") {
			return false;
		}
	});
};

Preprocessors Added in v3.0.0

Example: Drafts

Other pages in Configuration: