Detect if Element is a Web Component

By  on  

I've advocated for web components since before they became a spec, mostly inspired by the Dojo Toolkit's dijit framework. Empowering first class JavaScript widgets, as opposed to a mess of DIVs and templates, always made the most sense. Now that web components exist, and awesome frameworks like Ionic are based on them, I wanted to discover how to detect a web component, as opposed to a regular HTML element, with JavaScript. As it turns out, it's much easier than you'd think.

Assuming you have a reference to an element, it's as easy as detecting a dash in the element's tag:

function isWebComponent(element) {
  return element.tagName.includes("-");
}

The web component spec requires a dash in the HTMLElement's tagName, so detecting a web component is essentially nailed down to a string comparison.

If you haven't played with web components, I really hope you find the time. Having lived through decades of "widgets" and over-nesting of arbitrary DIVs and unreadable code, I've learned to appreciate these gems!

Recent Features

  • By
    CSS Gradients

    With CSS border-radius, I showed you how CSS can bridge the gap between design and development by adding rounded corners to elements.  CSS gradients are another step in that direction.  Now that CSS gradients are supported in Internet Explorer 8+, Firefox, Safari, and Chrome...

  • By
    Being a Dev Dad

    I get asked loads of questions every day but I'm always surprised that they're rarely questions about code or even tech -- many of the questions I get are more about non-dev stuff like what my office is like, what software I use, and oftentimes...

Incredible Demos

  • By
    Truly Responsive Images with responsive-images.js

    Responsive web design is something you hear a lot about these days. The moment I really started to get into responsive design was a few months ago when I started to realise that 'responsive' is not just about scaling your websites to the size of your...

  • By
    Create a Dojo Lightbox with dojox.image.Lightbox

    One of the reasons I love the Dojo Toolkit is that it seems to have everything.  No scouring for a plugin from this site and then another plugin from that site to build my application.  Buried within the expansive dojox namespace of Dojo is

Discussion

  1. Wouldn’t that just check whether it is a custom element? To my knowledge, custom elements can live on their own and do not have to be actual web components.

    • Šime Vidas

      Could you explain the difference between a custom element and a web component?

    • Jv

      My exact thought, Catalin! This isn’t really robust enough..

  2. Yaisiel

    I feel like that will not work if you declare your web component as a “customized built-in” (https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements#Customized_built-in_elements). That type of component is built on top of an existing element (like a for example) and the tag names don’t contain hyphens. I’m not sure, however, how many people would follow that approach in practice. It might be that, for the majority of the cases, checking for hyphens is enough.

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!