How can I create a custom HTML element with accessibility

Question

How can I create a custom HTML element that can be styled with CSS and have specific behaviors, such as click events, proper semantics, and accessibility? Are there any best practices for defining specific behaviors for custom HTML elements using event listeners? What are some examples of custom HTML elements that have been successfully implemented on websites

<!DOCTYPE html>
<html>
<head>
    <title>Custom HTML Element Example</title>
    <style>
        .custom-element {
            background-color: #ccc;
            padding: 10px;
            cursor: pointer;
        }
    </style>
</head>
<body>
    <custom-element >Click me</custom-element>

    <script>
        class CustomElement extends HTMLElement {
            constructor() {
                super();
                this.addEventListener('click', () => {
                    alert('You clicked the custom element!');
                });
            }
        }

        window.customElements.define('custom-element', CustomElement);
    </script>
</body>
</html>

element is not keyboard accessible

FYI: Your click only works here because you defined the component **after** ```` was parsed in the DOM. By default there is no DOM created in the ``constructor`` (try a ``document.createElement("custom-element")``; it will error. The ``connectedCallback`` tells you when the element is actually in the DOM, and that is when you can assign Events. — Danny '365CSI' Engelman, May 10 '23 at 14:48

score 0 · Accepted Answer · answered May 10 '23 at 14:54

FYI: Your click only works here because you defined the component after <custom-element> was parsed in the DOM. By default there is no DOM created in the constructor (try a document.createElement("custom-element"); it will error.

The connectedCallback tells you when the element is actually in the DOM, and that is when you can assign Events.

<style>
  .custom-element {
    background-color: #ccc;
    padding: 10px;
    cursor: pointer;
  }
</style>
</head>

<body>
  <custom-element>Click me</custom-element>

  <script>
    customElements.define('custom-element', class extends HTMLElement {
      //constructor() {
        //super();
        // only set properties or shadowDOM here
        // this element is NOT in the DOM yet!
      //}
      connectedCallback(){
        // might as well do oldskool inline clicks here
        // because (in principle) no other code in the page
        // should mess with this component
        this.onclick = () => alert("inline click!");

        this.addEventListener('click', () => {
          alert('You clicked the custom element!');
        });
      }
    });
  </script>

How can I create a custom HTML element with accessibility

1 Answers1