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Data Deep Merge

Contents

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).

Filename .eleventy.js
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 Jump to heading

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 Jump to heading

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 Jump to heading

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 Jump to heading

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.

Other pages in Data Cascade: