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Loading an external JS file using Gatsby

The Valley of Code

Your Web Development Manual

In the modern JavaScript Web Development workflow it’s quite common to install JavaScript via npm packages.

Sometimes however we must include an external JavaScript file, and modern tools might make this a little difficult.

In particular I had the need to include a video from Wistia in my site, and after a quick look everything looked quite more complicated than I wanted.

Wistia gave me this HTML snippet to embed:

<script src="" async></script><script src="" async></script><div class="wistia_responsive_padding" style="padding:56.25% 0 0 0;position:relative;"><div class="wistia_responsive_wrapper" style="height:100%;left:0;position:absolute;top:0;width:100%;"><div class="wistia_embed wistia_async_VIDEOURL seo=false videoFoam=true" style="height:100%;position:relative;width:100%"><div class="wistia_swatch" style="height:100%;left:0;opacity:0;overflow:hidden;position:absolute;top:0;transition:opacity 200ms;width:100%;"><img src="" style="filter:blur(5px);height:100%;object-fit:contain;width:100%;" alt="" aria-hidden="true" onload=";" /></div></div></div></div>

On a “normal” HTML site, maybe built with Hugo like I usually do, it would be dead simple.

I’d just add this code to my page.

But in a Gatsby page, which is a React component?

I looked at some plugins but no one really did what I wanted.

The solution is perhaps a bit “hacky”, but worked like a charm and I still feel I have control over what’s happening.

I added the HTML code as JSX, properly converting all the HTML attributes: class -> className, aria-hidden -> ariaHidden, and the styles - use a tool like to make it quick.

Then I added this code to the gatsby-browser.js file to add the scripts I needed, on page load:

const addScript = url => {
  const script = document.createElement("script")
  script.src = url
  script.async = true

export const onClientEntry = () => {
  window.onload = () => {
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