code-playground

Code Playground is a web component to display an editable and executable code section in a web page.

To use it, add a script tag pointing to the code for the component:

<script type="module" src="../dist/code-playground.min.js"></script>

Then add a <code-playground> tag in your page:

<code-playground>
  <div slot="javascript">console.log("Hello world")</div>
</code-playground>

Add one or more <div> with a slot attribute indicating the type of content: "javascript", "html" or "css".

If there are multiple "slots", each will be displayed in a separate tab or section.

If CodeMirror is included in the page, it will be used as the editor for the content. To include it, add these script tags to your page:

<script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.11/codemirror.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.11/mode/javascript/javascript.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.11/mode/xml/xml.min.js"></script>

If the attribute autorun=never is present, pres Run to execute the code after changing it.

To revert your changes and restore the initial content, press Reset.

The JavaScript source code is modified before execution to be executable in a 'sandbox':

• the console calls, such as console.log() are intercepted so they are displayed in the playground rather than in the browser's console
• the document.querySelector(), 'document.querySelectorAll() and 'document.getElementById() calls are also intercepted to respect the scope of the playground, that is using these calls you can also access content in the playground. This means you can also have multiple elements with the same ID in different playgrounds, and the correct one will be selected.
• if a style slot is provided, its content is injected as a CSS stylesheet before the script execution

<code-playground layout="stack" show-line-numbers>
  <style slot="style">
    .grey-zone {
      background: grey;
      height: 100px;
      width: 100%;
    }
  </style>
  <div slot="html">&lt;div class="grey-zone"&gt;&lt\div&gt;</div>
</code-playground>

• if a preamble slot is provided, it is inserted before the script.
• if a output-stylesheets attribute is provided, it is used to insert links to stylesheets in the output.
• the path of import directives can be modified as well. Add a <script> tag inside the component that defines a moduleMap variable that maps a module name to a URL. For example:

<code-playground>
  <script>
    moduleMap = {
      mathlive: "//unpkg.com/mathlive/dist/mathlive.min.mjs",
    };
  </script></code-playground>
  <div slot="javascript">import MathLive from 'mathlive';</div>
</code-playground>

will result in the "mathlive" module to be loaded from the "//unpkg.com/mathlive/dist/mathlive.min.mjs" URL;

Attributes and Properties

The attributes can be specified directly on the component, e.g.

<code-playground layout="stack">
  <div slot="javascript">...</div>
  <div slot="html">...</div>
</code-playground>

There are corresponding properties for the attributes which can be accessed via JavaScript.

Attribute	Property
layout		stack (each section is displayed in a column) or tabs (each section is displayed in a panel with a tab selector)
active-tab	activeTab	html, javascript or css: indicate which tab is visible if the layout is tab
show-line-numbers	showLineNumbers	true or false. If true, displays line numbers in the gutter of the source code.
button-bar-visibility	buttonBarVisibility	visible: always show the button bar, hidden: never show the button bar, auto: show the button bar when the content is modified
autorun	autorun	never: the Run button must be pressed to see changes, otherwise a number indicating a lag in millisecond between editing changes and re-running the playground