How to resolve this typescript error on global node.js object

Question

I am following this guide https://vercel.com/guides/nextjs-prisma-postgres to create a full stack app. Typescript is throwing an error in this snippet of code:

import { PrismaClient } from '@prisma/client';
let prisma: PrismaClient;

if (process.env.NODE_ENV === 'production') {
  prisma = new PrismaClient();
} else {
  if (!global.prisma) {
    global.prisma = new PrismaClient();
  }
  prisma = global.prisma;
}

export default prisma;

TypeScript is throwing a ts7017 on the global.prisma:

Element implicitly has an 'any' type because type 'typeof globalThis' has no index signature.

Can someone help me understand this and how to fix? I set 'strict' to false in the tsconfig for the meantime and that supressed the issue for the meantime, though I'm sure having it off defeats the purpose of TS.

Do you know how global.prisma is declared? If you don't have access to its declaration, have you tried casting it with global.prisma as PrismaClient? — Pablo
– Pablo, Commented Nov 5, 2021 at 9:04
I would just not use the global.. It's not even clear why there doing that in the first place.. strange!!! They even import later. import prisma from '../lib/prisma'; — Keith
– Keith, Commented Nov 5, 2021 at 9:17
Nikolas from the Prisma team here! We recommend the instantiation of PrismaClient in this way because otherwise the DB connection limit gets exhausted in development due to Next.js' hot reloading. Here's our docs page about this: prisma.io/docs/support/help-articles/… I'm checking back with some of our TypeScript engineers to see how this issue can be solved. — nburk
– nburk, Commented Nov 5, 2021 at 9:26

Joël · Accepted Answer · 2021-12-03 13:35:53Z

20

I could reproduce the same error with strict mode to true and @types/node package version 16

Update: see the other answer recommended from the docs here https://stackoverflow.com/a/69851359/1345244

This should work:

declare global {
  var prisma: PrismaClient; // This must be a `var` and not a `let / const`
}

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

if (process.env.NODE_ENV === "production") {
  prisma = new PrismaClient();
} else {
  if (!global.prisma) {
    global.prisma = new PrismaClient();
  }
  prisma = global.prisma;
}

export default prisma;

edited Dec 3, 2021 at 13:35

answered Nov 5, 2021 at 9:54

Joël

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1 Comment

Amir Alam Over a year ago

i was trying the same but i was adding const instead of let. i am confused why it didnt worked with const?

SebasWebDev · Accepted Answer · 2021-11-05 09:52:21Z

5

According to the docs you need to declare the variable global first:

import { PrismaClient } from '@prisma/client'

declare global {
  var prisma: PrismaClient | undefined
}

export const prisma =
  global.prisma ||
  new PrismaClient({
    log: ['query'],
  });

if (process.env.NODE_ENV !== 'production') global.prisma = prisma;

You can also have a separate file globals.d.ts with the declaration in it.

answered Nov 5, 2021 at 9:52

SebasWebDev

511 bronze badge

3 Comments

Alejandro Zapien Over a year ago

Can you explain a little more the purpose of writing the | undefined ?

SebasWebDev Over a year ago

The pipe in this case is used to separate the different types the variable prisma can potentially be. By adding ‘| undefined’ typescript will warn if the variable is used without checking if it’s defined.

Alejandro Zapien Over a year ago

thanks for the clarification and helping me understand :)

Michael · Accepted Answer · 2025-03-04 09:31:42Z

0

I tried this by creating a separate globals.d.ts file with the declaration in it, and it worked.

answered Mar 4 at 9:31

Michael

1

1 Comment

Community Mar 4 at 16:51

As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center.

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