How to deploy nestjs app to vercel

Create an api/restful.js file with the following content:

require("../dist/src/main");

Or create an api/restul.ts file with:

require("../src/main");

Create a vercel.json file with the following content:

{
  "framework": null,
  "outputDirectory": ".",
  "buildCommand": "npm run build",
  "functions": {
    "api/*.js": {
      "memory": 1024,
      "maxDuration": 10
    }
  },
  "rewrites": [
    {
      "source": "/api(.*)",
      "destination": "/api/restful"
    },
    {
      "source": "/(.*)",
      "destination": "/public"
    }
  ]
}

Deploy by executing vercel deploy or vercel deploy --prod.

Locally development:

1. You can just execute vercel dev -l 3100, which automatically loads the .env file. You may need to run npx nest build --watch together.
2. Execute dotenv npx nest start --watch which manually loads the .env file. I found --watch doesn’t work in this way.
3. Execute npx nest start --watch which needs to add the following content in your codes to load the .env file:

   export const isNestDev = !process.env.JWT_SECRET;
   if (isNestDev) {
     require("dotenv").config();
   }