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HTML includes using web components and iframes

This article is part of a series on HTML includes. Last week, we looked at how to include external HTML using iframes, and how to build a web component to fetch remote HTML.

Today, we’re going to combine the two techniques, courtesy of Andy Bell.

We’ll start with our custom include-html element.

<include-html path="about.html">
	<a href="about.html">Learn more about me.</a>

Inside the constructor() for our web component class, we’ll remove the #getHTML() method entirely.

Instead, we’ll use the Element.innerHTML property to inject an iframe with our path as the src. We’ll include the onload technique to pop the iframe content out into the main document.

 * The class constructor object
constructor () {

	// Always call super first in constructor

	// Get the source HTML to load
	let path = this.getAttribute('path');
	if (!path) return;

	// Render HTML
	this.innerHTML = `<iframe src="${path}" onload="this.before(...(this.contentWindow.document.body||this.contentWindow.document).children);this.remove()">`;


This provides us with an extra layer of resilience, and prevents use from having to make a fetch() call. We just work with what the browser already does.

You can download the source code on GitHub.

You’ll need to run a web server to make this work, which you can do using the command line or running a GUI tool like MAMP.

Tomorrow, we’ll learn how to use includes using compilers.