JavaScript Data Files {% addedin "0.5.3" %}

{% tableofcontents %}

The following applies to both:

• Global Data Files (*.js inside of your _data directory)
• Template and Directory Data Files (*.11tydata.js files that are paired with a template file or directory)

Using JS Data Files

You can export data from a JavaScript file to add data, too. This allows you to execute arbitrary code to fetch data at build time.

{% set codeContent %} export default ["user1", "user2"]; {% endset %} {% include "snippets/esmCjsTabs.njk" %}

If you return a function, we’ll use the return value from that function.

{% set codeContent %} export default function () { return ["user1", "user2"]; } {% endset %} {% include "snippets/esmCjsTabs.njk" %}

We use await on the return value, so you can return a promise and/or use an async function, too. Fetch your data asynchronously at build time!

{% set codeContent %} async function fetchUserData(username) { // do some async things return username; }

export default async function () { let user1 = await fetchUserData("user1"); let user2 = await fetchUserData("user2");

return [user1, user2];

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

Fetching data from a remote API

You’ll want to use Eleventy’s Fetch plugin to request and cache data from remote APIs. There is another example on Quick Tip #009—Cache Data Requests.

Arguments to Global Data Files

{% addedin "1.0.0" %} When using a callback function in your JavaScript Data Files, Eleventy will now supply any global data already processed via the Configuration API (eleventyConfig.addGlobalData) as well as the eleventy global variable.

{% set codeContent %} export default function (configData) { if (configData.eleventy.env.source === "cli") { return "I am on the command line"; }

return "I am running programmatically via a script";

} {% endset %} {% include "snippets/esmCjsTabs.njk" %}

Examples

• Example: Using GraphQL
• Example: Exposing Environment Variables
• Fetch GitHub star counts
• Caching remote images, Google Fonts CSS, and more on the Eleventy Fetch plugin docs

Example: Using GraphQL

This “Hello World” GraphQL example works out of the box with Eleventy:

{% set codeContent %} import { graphql, buildSchema } from "graphql";

// this could also be async function export default function () { // if you want to await for other things here, use async function var schema = buildSchema(type Query { hello: String });

var root = {
	hello: () => "Hello world async!",
};
return graphql(schema, "{ hello }", root);

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

Example: Exposing Environment Variables

You can expose environment variables to your templates by utilizing Node.js’ process.env property. (Related: Eleventy also supplies a few of its own Environment Variables)

• Learn how to set your own environment variables

Start by creating a Global Data file (*.js inside of your _data directory) and export the environment variables for use in a template:

_data/myProject.js

Saving this as myProject.js in your global data directory (by default, this is _data/) gives you access to the myProject.environment variable in your templates.

• Learn how to set a value for the MY_ENVIRONMENT environment variable

When MY_ENVIRONMENT is set, the value from myProject.environment will be globally available to be used in your templates. If the variable hasn’t been set, the fallback "development" will be used.

Template Usage

Working from our Inline CSS Quick Tip, we can modify the output to only minify our CSS if we’re building for production:

{% set codeBlock %}{% raw %}

{% endraw %}{% endset %} {{ codeBlock | highlight("html") | safe }}