How to achieve window.onload with Gatsby

I want to add a dynamic meta tags for my website using REST API, I want to achieve something like this: window.onload, If you notice the page is still loading until that function is done, I want that function to be the GET call for my meta tags.

Any ideas?

[ascorbic]

How about using react-helmet for the meta tags, and setting the values inside a useEffect hook? This will be run after hydration, so in your app, something like:

import React from "react"
import { Helmet } from "react-helmet"

export const App = ({ children }) => {
  const [metaTag, setMetaTag] = React.useState()

  React.useEffect(() => {
    const loadMetaTag = async () => {
      const tag = await getMetaTag()
      setMetaTag(tag)
    }
    loadMetaTag()
  }, [])

  return (
    <>
      <Helmet>
        {metaTag && <meta name="description" content={metaTag} />}
      </Helmet>
      {children}
    </>
  )
}

[vladar]

How do you use Gatsby in this situation? Do you have a separate site for each company or do you have a single Gatsby site?

And what metatags are you going to update (and for which purpose)? I am asking because updating some of them via javascript makes little sense (i.e. SEO-related).

It is still not entirely clear what you are trying to achieve, so please share a bit more details.

Also, you can always customize html if you have to.