Data Deep Merge

Contents

Example
- Without Deep Data Merge
- With Data Deep Merge
Using the override: prefix

Use a full deep merge when combining the Data Cascade. This will use something similar to lodash.mergewith to combine Arrays and deep merge Objects, rather than a simple top-level merge using Object.assign.

Read more at Issue #147. As of Eleventy 1.0 this defaults to enabled (but API still exists for opt-out).

eleventy.config.js

ESM CommonJS

export default function (eleventyConfig) {
	// defaults to true in 1.0, use false to opt-out
	eleventyConfig.setDataDeepMerge(false);

	// requires opt-in for 0.x
	eleventyConfig.setDataDeepMerge(true);
};

module.exports = function (eleventyConfig) {
	// defaults to true in 1.0, use false to opt-out
	eleventyConfig.setDataDeepMerge(false);

	// requires opt-in for 0.x
	eleventyConfig.setDataDeepMerge(true);
};

Note that all data stored in the pagination variable is exempted from this behavior (we don’t want pagination.items to be merged together).

Example

Filename my-template.md

---
title: This is a Good Blog Post
tags:
  - CSS
  - HTML
layout: my-layout.njk
eleventyNavigation:
  key: my-key
---

Filename _includes/my-layout.njk

---
title: This is a Very Good Blog Post
author: Zach
tags:
  - JavaScript
eleventyNavigation:
  parent: test
---

Without Deep Data Merge

Results in the following data available in my-template.md:

Syntax JavaScript

{
	"title": "This is a Good Blog Post",
	"author": "Zach",
	"tags": ["CSS", "HTML"],
	"eleventyNavigation": {
		"key": "my-key"
	}
}

With Data Deep Merge

With this enabled, your data structure will look like this when my-template.md is rendered:

Syntax JavaScript

{
	"title": "This is a Good Blog Post",
	"author": "Zach",
	"tags": ["CSS", "HTML", "JavaScript"],
	"eleventyNavigation": {
		"key": "my-key",
		"parent": "test"
	}
}

Using the `override:` prefix

Use the override: prefix on any data key to opt-out of this merge behavior for specific values or nested values.

Filename posts/posts.json

{
	"tags": ["posts"]
}

Filename posts/firstpost.md

---
override:tags: []
---

Even though normally the posts/firstpost.md file would inherit the posts tag from the directory data file (per normal data cascade rules), we can override the tags value to be an empty array to opt-out of this behavior.

Data Deep Merge

Example

Without Deep Data Merge

With Data Deep Merge

Using the override: prefix

Other pages in Data Cascade:

Using the `override:` prefix