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How can I ensure my custom web component updates correctly when its attributes change in different browsers?

Asked on Nov 15, 2025

Answer

To ensure your custom web component updates correctly when its attributes change, you should use the "attributeChangedCallback" lifecycle method. This method is part of the Web Components API and is supported across modern browsers.
<!-- BEGIN COPY / PASTE -->
        class MyComponent extends HTMLElement {
            static get observedAttributes() {
                return ['my-attribute'];
            }

            constructor() {
                super();
                this.attachShadow({ mode: 'open' });
                this.shadowRoot.innerHTML = `<p>Initial content</p>`;
            }

            attributeChangedCallback(name, oldValue, newValue) {
                if (name === 'my-attribute') {
                    this.shadowRoot.querySelector('p').textContent = `Attribute changed to: ${newValue}`;
                }
            }
        }

        customElements.define('my-component', MyComponent);
        <!-- END COPY / PASTE -->
Additional Comment:
  • The "observedAttributes" static method returns an array of attribute names that the component should observe for changes.
  • The "attributeChangedCallback" method is called whenever one of the observed attributes changes.
  • In the example, when "my-attribute" changes, the content of the paragraph inside the shadow DOM is updated.
  • Ensure your component is defined using "customElements.define" for it to be recognized by the browser.
✅ Answered with JavaScript best practices.
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