[FIXED] How to get environment variables on client side with Next.js?

Issue

I want to read environment variable into Next.js, how to pass data into datadogRum.init?

// _app.tsx

import React from "react";
import { useEffect } from "react";
import type { AppProps } from "next/app";
import { datadogRum } from "@datadog/browser-rum";

export default function App({ Component, pageProps }: AppProps) {
  useEffect(() => {
    datadogRum.init({
      applicationId: applicationID, // can't use process.env.NEXT_PUBLIC_DATADOG_APPLICATION_ID directly here
      ...
    });

    datadogRum.startSessionReplayRecording();
  });

  return (
    ...
  );
}

App.getInitialProps = async () => {
  return {
    applicationID: process.env.NEXT_PUBLIC_DATADOG_APPLICATION_ID,
  };
};

This way can't get the applicationID value.

Solution

You don't need to pass the environment variable from getInitialProps. You can access it directly inside the useEffect, you just need to make sure process.env.NEXT_PUBLIC_DATADOG_APPLICATION_ID is defined before initialising datadogRum.init to avoid typings conflicts.

export default function App({ Component, pageProps }: AppProps) {
    useEffect(() => {
        if (typeof process.env.NEXT_PUBLIC_DATADOG_APPLICATION_ID !== "undefined")
            datadogRum.init({
                applicationId: process.env.NEXT_PUBLIC_DATADOG_APPLICATION_ID
                ...
            });

            datadogRum.startSessionReplayRecording();
        }
    });

    return (
        ...
    );
}

Answered By - juliomalves

Answer Checked By - Dawn Plyler (PHPFixing Volunteer)