Logger Methods

• Nest comes with a built-in text-based logger which is used during application bootstrapping and several other circumstances such as displaying caught exceptions (i.e., system logging)

• You can fully control the behavior of the logging system, including any of the following:

  • disable logging entirely
  • specify the log level of detail (e.g., display errors, warnings, debug information, etc.)
  • override timestamp in the default logger (e.g., use ISO8601 standard as date format)
  • completely override the default logger
  • customize the default logger by extending it
  • make use of dependency injection to simplify composing and testing your application

    import { Logger } from "@nestjs/common";
   
    export class BookService {

        private readonly logger = new Logger(BookService.name);

        addBook(name: string) {
            try{
                this.logger.log('adding book to db...');
                this.logger.debug("Book name:{}", name)
            }catch(err){
                logger.error("error", err);
                logger.error("Unable to add book :{}", err.message);
            }
        }
       
    }

• Logs

[Nest] 19096   - 01/02/2024, 7:12:59 AM   [NestFactory] Starting Nest application...

Disable Logging

• main.ts

    const app = await NestFactory.create(AppModule, {
         logger: false,
    });
    await app.listen(3000);

Enable Logging

    const app = await NestFactory.create(AppModule, {
         logger: ['error', 'warn'],
    });
    await app.listen(3000);

• Values in the array can be any combination of 'log', 'fatal', 'error', 'warn', 'debug', and 'verbose'.