eleventy-plugin-console-plus

Console Plus is a Eleventy (11ty) plugin that adds a shortcode for debugging your templates, objects, and data. It logs to your HTML output, your terminal, and your browser console—all at once, with beautiful formatting and deep customization.

The HTML output uses a custom Web Component (<console-plus>) that provides an interactive, collapsible JSON viewer with advanced features like type labels, hover paths, and expandable nodes.

If you've ever tried to debug collections or any other complex object in Eleventy this is for you.

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✨ Features

• Interactive Web Component: Uses <json-viewer> custom element for rich HTML output
• Multi-destination logging: Outputs to HTML, terminal, and browser console simultaneously
• Advanced JSON viewer: Collapsible nodes, type labels, key paths on hover, and expand controls
• Robust data handling: Handles circular references, functions, symbols, BigInts, Dates, and undefined
• Security features: XSS prevention, input validation, and malicious content detection
• Performance optimized: Memoization, debouncing, and memory management
• Browser compatibility: Fallback modes for environments without Shadow DOM support
• Flexible configuration: Hide or replace keys, control output destinations, and customize viewer appearance
• Works with Eleventy v3+: Full ESM & CJS support

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🚀 Installation

npm install eleventy-plugin-console-plus

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⚡ Quick Start

In your eleventy.config.js :

ES Modules Configuration

import { consolePlus } from 'eleventy-plugin-console-plus';

export default function(eleventyConfig) {
  eleventyConfig.addPlugin(consolePlus);
}

CommonJS Configuration

Since this plugin is an ES module, you'll need to use dynamic import() in CommonJS configuration files:

module.exports = async function(eleventyConfig) {
  const { consolePlus } = await import('eleventy-plugin-console-plus');
  eleventyConfig.addPlugin(consolePlus);
};

In your template:

  {% console  { string: "Hello, World!", number: 123 } %}

Outputs to your HTML as an interactive web component:

Collections Example

Debug your Eleventy collections data:

  {% console collections %}

This will display all your content organized by collection in the interactive JSON viewer.

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🛠️ Usage

An object, string, variable or array is required as the first argument. A title and configurantion options are optional.

{% console <value - required >, <"title" — optional>, <{options} — optional> %}

Examples

Assume we have the following variable:

 obj = {
        string: "Some String",
        number: 42,
        boolean: true,
        nullValue: null,
        undefinedValue: undefined,
        array: [1, 2, 3],
        object: { key: "value" },
        nestedArray: [{ a: 1 }, { b: 2 }],
        nestedObject: { inner: { key: "innerValue" } },
        template: { key1: "value1", key2: "value2", array: [1, 2, 3] }
 		}

1. With a Title

{% console obj, "My Object" %}

4. Show Types and Default Expanded

{% console obj, { showTypes: true, defaultExpanded: true } %}

This will display type labels and expand all nodes by default in the web component viewer.

2. Showing Template Keys

By default any key named template has it's value removed for performance reasons. Eleventy puts a TON of stuff in the template key of your page and in collections. You almost never need it. But if you do...

{% console obj, { showTemplate: true } %}

3. Hiding or replacing keys

Similarly sometimes your data contains a large nested structure that you're not interested in. You can exclude or replace this in the output with...

{% console myObject, { removeKeys: ["nestedArray", { keyName: "nestedObject", replaceString: "***" }] } %}

🔧 Web Component Features

The <console-plus> web component provides several interactive features:

• Collapsible nodes: Click the arrow (▶/▼) to expand/collapse objects and arrays
• Type labels: Enable showTypes: true to see data type indicators
• Hover paths: Enable pathsOnHover: true to see key paths when hovering
• Default expansion: Use defaultExpanded: true to show all content expanded
• Visual controls: Enable showControls: true for additional UI controls
• Custom styling: Adjust indentWidth for spacing preferences

Browser Compatibility

The web component includes fallback support for environments without Shadow DOM:

• Modern browsers: Uses Shadow DOM for encapsulation
• Legacy browsers: Falls back to direct DOM manipulation
• No JavaScript: Displays as plain text if JavaScript is disabled

⚙️ Configuration

You can pass a configuration object when you add the plugin.

In your eleventy.config.js:

import { consolePlus } from 'eleventy-plugin-console-plus';

export default function(eleventyConfig) {
  eleventyConfig.addPlugin(consolePlus, { 
  	logToHtml: true,           // output to HTML
  	logToTerminal: false,      // output to terminal
  	logToBrowserConsole: false,// output to browser console
  	showTemplate: true         // always show template key
  } );
}

These options will apply to all instances of the shortcode. Unless you overide them on a case by case basis.

{% console obj, "My Object", { showTemplate: false, logToTerminal: true,  } %}

template will not be shown and output will be logged to terminal in this instance of the shortcode.

You can see the full configurations options below.

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⚙️ Options Reference

Option	Type	Default	Description
logToHtml	boolean	true	Output to HTML viewer
logToTerminal	boolean	true	Output to terminal
logToBrowserConsole	boolean	true	Output to browser console
title	string	""	Optional title for output
colorizeConsole	boolean	true	Colorize terminal output
depth	number	8	Terminal object depth
breakLength	number	60	Terminal line break length
showTemplate	boolean	false	Show 'template' keys in objects
maxCircularDepth	number	1	Max depth for circular references
removeKeys	array	[]	Keys to remove/replace (string or {keyName, replaceString})
showTypes	boolean	false	Show type labels in viewer
defaultExpanded	boolean	false	Expand nodes by default in viewer
pathsOnHover	boolean	false	Show key path hover panel in viewer
showControls	boolean	false	Show UI controls in viewer
indentWidth	number	6	Indentation width in px in viewer

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🖼️ Screenshots

HTML output

Browser Console output

Terminal output

Notable Updates

2.0.0 (latest) — Complete rewrite and major feature release:

• Web Component Architecture: Interactive <console-plus> custom element with Shadow DOM
• Enhanced Security: XSS prevention, input validation, and malicious content detection
• Performance Optimizations: Memoization, debouncing, memory management, and virtual rendering
• Browser Compatibility: Fallback modes for environments without Shadow DOM support
• Comprehensive Testing: 115+ tests covering security, performance, error handling, and browser compatibility
• Improved Error Handling: Graceful degradation and detailed error messages
• ES Module Only: Simplified build process, removed CommonJS build
• Dynamic Import Support: Clear documentation for CommonJS config usage
• Reduced Package Size: Eliminated Rollup build step and generated files
• Collections Example: Added {% console collections %} for debugging Eleventy collections

1.0.0 — Rewritten from scratch, improved HTML output, better plugin naming

0.1.1 — Added logging to browser console & option to wrap line length

📄 License

MIT