How to include local javascript on a Gatsby page?

There are many ways to add scripts in GatsbyJS...

To execute a script on a specific page

• create a stateless ScriptComponent.js file and place it inside your /src folder.

• in your ScriptComponent.js use require() to execute the script inside useEffect() like this:

  const ScriptComponent = ({
   src, // if internal,put a path relative to this component
   onScriptLoad = () => {}, // cb
   appendToHead = false,
   timeoutDuration = 10, 
   defer = false,
   isExternal = false,
  }) => {
  
   useEffect(() => {
    setTimeout(() => {
     if (isExternal) {
      const script = document.createElement('script');
      script.src = src;
      script.onload = onScriptLoad;
  
       defer
        ? script.defer = true
        : script.async = true;
  
       appendToHead
        ? document.head.appendChild(script)
        : document.body.appendChild(script);
      } else { // for internal scripts
       // This runs the script
       const myScript = require(src);
      }
     }, timeoutDuration);
    }, []);
  
   return null;
  };
  

• To run it on client-side, you could check the window object inside your script.js file if you didn't run it in useEffect:

   if(typeof window !== 'undefined' && window.document) {
      // Your script here...
   }
  

• finally, go to the page you want to execute the script in it (e.g. /pages/myPage.js ), and add the component <ScriptComponent />

If you want to execute a script globally in (every component/page) you could use the html.js file.

• first, you'll have to extract the file (in case you didn't) by running:

cp .cache/default-html.js src/html.js

• inside your html.js file:

<script dangerouslySetInnerHTML= {{ __html:`
  // your script here...
  // or you could also reuse the same approach as in useEffect above
`}} />

Just create gatsby-ssr.js file on root folder

and add the following pattern for your scripts folder

import React from 'react'

export const onRenderBody = ({ setPostBodyComponents }) => {
  setPostBodyComponents([
    <script
      key="https://code.jquery.com/jquery-3.2.1.slim.min.js"
      src="https://code.jquery.com/jquery-3.2.1.slim.min.js"
      integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
      crossOrigin="anonymous"
      defer
    />,
    <script
      key="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"
      src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"
      integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q"
      crossOrigin="anonymous"
      defer
    />,
    <script
      key="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"
      src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"
      integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl"
      crossOrigin="anonymous"
      defer
    />
  ])
}

Then, you at the end of dom you'll see the links to scripts

If you'd like to use a Gatsby plugin, which to me is no different from using an external library like Helmet (plugins are npm packages after all), you could use gatsby-plugin-load-script.

You can provide either the url to the src attribute or a local path. If you're going to store your JS in a local file such as some-minified-js.min.js - make sure to store in the static directory at the root of your project.

Once you do this, you can access via the global object:

global.<object or func name here>

For example, I was trying to include a very small JS library via a minified file, so I stored the file in /static/my-minified-library.min.js and then:

1. Installed the plugin: npm i --save gatsby-plugin-load-script
2. Added this to my gatsby-config.js

plugins: [
    {
      resolve: "gatsby-plugin-load-script",
      options: {
        src: "/my-minified-library.min.js",
      },
    },
  ],

3. Accessed in my react component like so:

useEffect(() => {
  const x = new global.MyImportedLibraryObject();
}, []}

You can do this very easily with the Gatsby plugin "gatsby-plugin-load-script."

Simply do this:

1. Create a folder named static at the root of your gatsby app
2. Place your script in it
3. Add the following configuration in gatsby-config.js

    {
      resolve: 'gatsby-plugin-load-script',
      options: {
        src: '/test-script.js', // Change to the script filename
      },
    },

Gatsby uses html.js in the src folder. Not index.html like most react projects.

Example html.js file:

import React from "react"
import PropTypes from "prop-types"

export default class HTML extends React.Component {
  render() {
    return (
      <html {...this.props.htmlAttributes}>
        <head>
          <meta charSet="utf-8" />
          <meta httpEquiv="x-ua-compatible" content="ie=edge" />
          <meta
            name="viewport"
            content="width=device-width, initial-scale=1, shrink-to-fit=no"
          />
          {this.props.headComponents}
        </head>
        <body {...this.props.bodyAttributes}>
          {this.props.preBodyComponents}
          <div
            key={`body`}
            id="___gatsby"
            dangerouslySetInnerHTML={{ __html: this.props.body }}
          />
          {this.props.postBodyComponents}
        </body>
      </html>
    )
  }
}

HTML.propTypes = {
  htmlAttributes: PropTypes.object,
  headComponents: PropTypes.array,
  bodyAttributes: PropTypes.object,
  preBodyComponents: PropTypes.array,
  body: PropTypes.string,
  postBodyComponents: PropTypes.array,
}

For adding custom Javascript using dangerouslySetInnerHTML inside src/html.js:

<script
  dangerouslySetInnerHTML={{
    __html: `
            var name = 'world';
            console.log('Hello ' + name);
        `,
  }}
/>

You can try adding your js there but, note that your js may not work as expected. You can always look into react-helmet for more dynamic apps and adding scripts to <head>.

Gatsby Documentation: https://www.gatsbyjs.org/docs/custom-html/

I'm not sure if anyone still needs this answer, but here it goes:

The answer by Elliot Marques is excellent. If you need it for a local file, upload the script to Github and use a service like JSDelivr. It saves a lot of time and stress.

React works with dynamic DOM. But for rendering it by browser, your web server should send a static index page, where React will be included as another script tag.

So, take a look on your index.html page, which you can find in public folder. There you could insert your script tag in the header section, for example.