HTML Templates for Web Components — Complete Guide
DodaTech
Updated 2026-06-28
1 min read
In this tutorial, you will learn about HTML Templates for Web Components. We cover key concepts, practical examples, and best practices to help you master this topic.
HTML Templates provide reusable markup fragments that Web Components clone for efficient rendering, with slots for content projection.
What You'll Learn
- How to use template elements in Web Components
- How to combine templates with Shadow Dom
- How to populate template content with data
- Performance benefits of template cloning
Why It Matters
Templates separate markup from JavaScript. They are parsed once and cloned efficiently. Combined with Shadow DOM, they create clean component architectures.
flowchart LR A[Define Template] --> B[ in HTML] B --> C[template.content.cloneNode] C --> D[shadowRoot.appendChild] D --> E[Component renders]
Template + Shadow DOM
class TemplateCard extends HTMLElement {
constructor() {
super();
const template = document.getElementById('card-template');
const shadow = this.attachShadow({ mode: 'open' });
shadow.appendChild(template.content.cloneNode(true));
}
connectedCallback() {
this.shadowRoot.querySelector('.title').textContent = this.getAttribute('title');
this.shadowRoot.querySelector('.desc').textContent = this.getAttribute('description');
}
}
customElements.define('template-card', TemplateCard);
Inline Template Definition
class InlineTemplate extends HTMLElement {
constructor() {
super();
this.attachShadow({ mode: 'open' });
}
connectedCallback() {
const template = document.createElement('template');
template.innerHTML = `
<style>
.box { border: 2px solid #3498db; padding: 16px; border-radius: 8px; }
h3 { margin: 0 0 8px; color: #3498db; }
</style>
<div class="box">
<h3><slot name="title"></slot></h3>
<slot></slot>
</div>
`;
this.shadowRoot.appendChild(template.content.cloneNode(true));
}
}
customElements.define('inline-template', InlineTemplate);
Common Mistakes
- Forgetting .cloneNode(true) — using the template content directly causes it to be empty for subsequent clones
- Modifying template content instead of the clone
Practice Questions
- Why use templates instead of innerHTML? Templates are parsed once and cloned, which is faster for repeated use.
- Must you deep clone template content? Yes. cloneNode(true) copies all children.
Mini Project
Build a data table component that uses a template for its row structure. Accept columns and rows as attributes/properties. Clone the template for each row.
What's Next
Lesson 9: Template Instantiating
Built by the developers of DodaTech
Doda Browser, DodaZIP & Durga Antivirus Pro