Suggested fix for "Best practice for instantiating PrismaClient with Next.js"

The code provided in https://www.prisma.io/docs/support/help-articles/nextjs-prisma-client-dev-practices generates an error with TypeScript in strict mode.

I would suggest something like this instead:

import { PrismaClient } from "@prisma/client";

// add prisma to the NodeJS global type
interface CustomNodeJsGlobal extends NodeJS.Global {
    prisma: PrismaClient;
}

// prevent multiple instances of Prisma Client in development
declare const global: CustomNodeJsGlobal;
const prisma = global.prisma || new PrismaClient();
if (process.env.NODE_ENV === "development") global.prisma = prisma;
export default prisma;

[CapKnoke]

Is there a similar workaround for vanilla js? I guess you could just declare it as a global var while in development, but is there a nice way of doing it conditionally like the ts example provided?

[trentprynn]

In case anyone runs into this while updating @types/node to version 16, I got around this error by replacing the above code (which works with @types/node<16) with the following

import { PrismaClient } from '@prisma/client'

// add prisma to the NodeJS global types to
// prevent multiple instances of prisma client
// get created by hot-reloading in development
declare global {
    var prisma: PrismaClient
}

const prisma = global.prisma || new PrismaClient()

if (process.env.NODE_ENV === 'development') {
    global.prisma = prisma
}

export default prisma

You can see it in context here where I’m using prisma for database interaction for an open source habit tracking web app I’m working on

EDIT: The documentation is now updated with a similar (probably better) solution