{% tableofcontents "open" %}

• Related languages: JSX, TypeScript, MDX
• Front matter is not supported in JavaScript files. Use a data export instead.

Eleventy supports many different types of JavaScript content that will be parsed as Eleventy templates. They are comprehensively described below.

Raw Values

Raw values will not have access to Data or JavaScript Template Functions. Use a function that returns a value instead.

String

{% set codeContent %} export default "

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Or template literals:

{% set codeContent %} export default <p>These can span multiple lines!</p>; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Buffer

Some templating libraries return Buffers (e.g. viperHTML).

{% set codeContent %} export default Buffer.from("

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Promise

{% set codeContent %} export default new Promise((resolve, reject) => { setTimeout(function () { resolve("

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Function

Can return any raw value (e.g. String, Buffer, Promise). Use template literals to embed data values without having to concatenate strings!

{% set codeContent %} export default function (data) { return <p>${data.name}</p>; }; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

De-structuring syntax is a little bit easier to read:

{% set codeContent %} export default function ({ name }) { return <p>${name}</p>; }; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Maybe you like arrow functions:

{% set codeContent %} export default ({ name }) => <p>${name}</p>; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

async functions work too:

{% set codeContent %} const getAnAsyncThing = require("./lib/asyncThing");

export default async function (data) { return <p>${await getAnAsyncThing()}</p>; }; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Classes

Eleventy looks for classes that have a render method and uses render to return the content of the template. render methods can be async.

render can return any raw value (e.g. String, Buffer, Promise).

{% set codeContent %} class Test { // or async render({name}) { render({ name }) { return <p>${name}</p>; } }

export default Test; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Optional data Method

{% callout "info" %}Front Matter is not supported in JavaScript template types. Use data methods instead! Additionally, there are more alternative options in the Data Cascade.{% endcallout %}

This data acts as Front Matter for the template and similarly to Front Matter will take precedence over all other data in the data cascade. The data method can be asynchronous async data() or it can be a getter get data().

{% set codeContent %} class Test { // or async data() { // or get data() { data() { return { name: "Ted", layout: "teds-rad-layout", // … other front matter keys }; }

render({ name }) {
	// will always be "Ted"
	return `<p>${name}</p>`;
}

}

export default Test; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Permalinks

The permalink data key will work here. Permalinks can be a raw value (e.g. String, Buffer, Promise) or a Function that returns any raw value.

Permalink String

{% set codeContent %} class Test { data() { return { // Writes to "/my-permalink/index.html" permalink: "/my-permalink/", }; }

render(data) {
	/* … */
}

}

export default Test; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Permalink Function

Permalink Functions can return any raw value (e.g. String, Buffer, Promise).

{% set codeContent %} class Test { data() { return { key: "hello", // Writes to "/my-permalink/hello/index.html" permalink: (data) => /my-permalink/${data.key}/, }; }

render(data) {
	/* … */
}

}

export default Test; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Permalink Function using a Filter

Universal filters, shortcodes, and other JavaScript Template Functions work here and are exposed on this. Read more about Eleventy provided Universal Filters.

{% set codeContent %} class Test { data() { return { title: "This is my blog post title", // Writes to "/this-is-my-blog-post-title/index.html" permalink: function (data) { return /${this.slug(data.title)}/; }, }; }

render(data) {
	/* … */
}

}

export default Test; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Markdown and JavaScript

Yes, you can use JavaScript as your preprocessor language for Markdown. Read more about templateEngineOverride.

{% set codeContent %} class Test { data() { return { myName: "Zach", templateEngineOverride: "11ty.js,md", }; }

render(data) {
	return `# This is ${data.myName}`;
}

}

export default Test; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

{% callout "info" %}While templateEngineOverride: 11ty.js,md works to add markdown support, the special behavior of JavaScript templates does not allow other template engines to be supported here (e.g. templateEngineOverride: njk,md). One workaround is to use the Render Plugin.{% endcallout %}

JavaScript Template Functions

A JavaScript Template Function allows you to extend your JavaScript templates with extra functionality. If you add any Universal Filters or Shortcodes, they will be exposed as JavaScript Template Functions.

{% set codeContent %} export default function(eleventyConfig) { eleventyConfig.addJavaScriptFunction("myFunction", function(a, b) { /* … */ }); }; {% endset %} {% include "snippets/configDefinition.njk" %}

js-fn-example.11ty.js

${this.myFunction(data.a, data.b)}

Asynchronous JavaScript Template Functions

This works the same as any async JavaScript function or function that returns a Promise.

This is the same as the example above but adds async before the function.

{% set codeContent %} export default function(eleventyConfig) { eleventyConfig.addJavaScriptFunction("myAsyncFunction", async function(a, b) { /* … */ }); }; {% endset %} {% include "snippets/configDefinition.njk" %}

This is the same as the example above but adds await before the function is called.

{% codetitle "js-async-fn-example.11ty.js" %}

{% set codeContent %} export default async function (data) { return <h1>${await this.myAsyncFunction(data.a, data.b)}</h1>; }; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Warning about Arrow Functions

{% callout "warn" %} Note that by definition (read on MDN) arrow functions do not have access to this, so any use of JavaScript Functions inside of an arrow function template will throw an error. {% endcallout %}

{% codetitle "js-arrow-fn-example.11ty.js" %}

{% set codeContent %} export default (data) => { // Using this in an arrow function will throw an error! return <h1>${this.myFunction(data.a, data.b)}</h1>; }; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Relationship to Filters and Shortcodes

Any universal filters or shortcodes will also be available as JavaScript Template Functions.

{% set codeContent %} export default function(eleventyConfig) { // Universal filters (Adds to Liquid, Nunjucks, 11ty.js) eleventyConfig.addFilter("myFilter", function(myVariable) { /* … */ });

// Universal Shortcodes (Adds to Liquid, Nunjucks, 11ty.js) eleventyConfig.addShortcode("user", function(firstName, lastName) { /* … */ });

// Universal Paired Shortcodes (Adds to Liquid, Nunjucks, 11ty.js) eleventyConfig.addPairedShortcode("pairedUser", function(content, firstName, lastName) { /* … */ }); }; {% endset %} {% include "snippets/configDefinition.njk" %}

{% codetitle "universal-examples.11ty.js" %}

{% set codeContent %} export default function (data) { return `

${this.myFilter(data.myVar)}

${this.user(data.firstName, data.lastName)}

${this.pairedUser( `Here is some more content`, data.firstName, data.lastName )}

Access to page data values {% addedin "0.11.0" %}

If you aren’t using an arrow function, JavaScript Functions (and Nunjucks, Liquid Shortcodes) will have access to Eleventy page data values without needing to pass them in as arguments.

{% set codeContent %} export default function (eleventyConfig) { eleventyConfig.addJavaScriptFunction("myFunction", function () { // Available in 0.11.0 and above console.log(this.page);

	// For example:
	console.log(this.page.url);
	console.log(this.page.inputPath);
	console.log(this.page.fileSlug);
});

}; {% endset %} {% include "snippets/configDefinition.njk" %}