Add a loader to gatsby website

I've been lately looking for some tricks to add a custom loading spinner to gatsby website without using the nProgress plugin that gatsby provide in the documentation, neither using the gatsby-browser.js file and calling browser Api's such as onRouteUpdate and onInitialClientRender, after trying few approaches the best one that performs as expected is made by useEffect hook, so here is the way to do that :

Prepare your svg spinner :

you can pick one from the examples provided in this link , copy it's code and create a file loadingSpinner.svg inside your assets file, and past the code there .

Create a file Loader.js :

in this file import your svg spinner and create a loader component :

import loadingSpinner from "assets/loadingSpinner.svg"


function Loader (){

  return (
    <div style={{
         position : "fixed",
         display : "flex",
         width : "100vw",
         height : "100vh",
         justifyContent : "center",
         alignItems : "center",
         zIndex : 600,
         backgroundColor : "#FFF"
         }}
    >
        <img src={loadingSpinner} 
             alt="loader" 
             width="150px" 
             height="150px"
        />
    </div>
  )
}
export default Loader

Note : you can change the color and size of the spinner in the svg file .

Add the Loader to html.js file:

import the Loader component in your html.js file, and put it inside a div tag just below the opening body tag, and give that div an id :

    <div id="full-page-loader">
       <Loader />
    </div>

at this point, the loader component will be displayed permanently whenever you run the website, we will figure this out in the next step .

Control the Loader component:

in the Layout.js file, get the loader component by it's id inside a the useEffect hook and delete it when the Layout file get rendered, just like this :

useEffect(() => {
    try {
      const element = document.getElementById("full-page- 
      loader")
      if (element) element.parentNode.removeChild(element)
    } catch(error) {
      console.log(error)
    }
  })

Note : we must use try catch block, so we can test our code while it's being executed, using just a normal if statement won't work and it will return a property of null error either for parentNode or the removeChilde method .