<pretty-json> HTML Custom Element

See the live demo

<pretty-json> is an HTML custom element that allows you to render JSON objects in HTML documents with human-readable formatting and expandable interaction for browsing deep JSON structures.

Usage

Include pretty-json-custom-element/index.js in your HTML page and use the HTML custom element as follows:

<script defer src="https://unpkg.com/pretty-json-custom-element/index.js"></script>
<pretty-json>
{
  "hello": "world",
  "value": 42,
  "enabled": true,
  "extra": null,
  "nested": { "key": "value" }
}
</pretty-json>

Your JSON will be rendered as a human-readable format:

Features

• Outputs a valid JSON string that can be copied and pasted into a JSON file
• HTML Custom Element without any dependencies, works in any modern browser
• No need to install any dependencies or build tools, just drop the script in your HTML and start using it
• Allows a high level of customization using CSS variables
• Display large JSON objects with expandable and collapsible sections
• Supports truncating very large strings and arrays with an ellipsis

To-do List

• [ ] Support grouping very large arrays

Attributes

You can customize the rendering of the JSON object by setting the following attributes on the <pretty-json> element:

expand

By default, the JSON object is rendered expanded up to 1 level deep. You can set the expand attribute to a number to expand the JSON object up to that level deep:

<pretty-json expand="2">{"hello": {"world": "!"}}</pretty-json>

Collapsed by default

You can set the expand attribute to 0 to render the JSON object collapsed by default:

<pretty-json expand="0">{"hello": {"world": "!"}}</pretty-json>

truncate-string

By default, strings longer than 500 characters are truncated with an ellipsis. You can set the truncate-string attribute to a number to truncate strings longer than that number of characters:

<pretty-json truncate-string="10">
  {"hello": "long string that will be truncated"}
</pretty-json>

Customization

You can customize the appearance of the rendered JSON using CSS variables:

pretty-json {
  --key-color: #cc0000;
  --arrow-color: #737373;
  --brace-color: #0030f0;
  --bracket-color: #0030f0;
  --string-color: #009900;
  --number-color: #0000ff;
  --null-color: #666666;
  --boolean-color: #d23c91;
  --comma-color: #666666;
  --ellipsis-color: #666666;

  --indent: 2rem;
}

/* Also handle the dark mode */
@media (prefers-color-scheme: dark) {
  pretty-json {
    --key-color: #f73d3d;
    --arrow-color: #6c6c6c;
    --brace-color: #0690bc;
    --bracket-color: #0690bc;
    --string-color: #21c521;
    --number-color: #0078b3;
    --null-color: #8c8888;
    --boolean-color: #c737b3;
    --comma-color: #848181;
    --ellipsis-color: #c2c2c2;
  }
}

Development

To run the development server:

yarn install
yarn start

Running tests

This repository uses Playwright for testing.

To run the tests:

yarn test