LogLayer

Getting Started ​

LogLayer is designed to work seamlessly across both server-side and browser environments. However, individual transports and plugins may have specific environment requirements, which is indicated on their respective page.

Installation ​

Node.js ​

sh
npm install loglayer
sh
pnpm add loglayer
sh
yarn add loglayer

Deno ​

For Deno, you can use npm: specifiers or import maps:

Using npm: specifiers:

typescript
import { LogLayer } from "npm:loglayer@latest";

Using import maps (recommended):

json
// deno.json
{
  "imports": {
    "loglayer": "npm:loglayer@latest"
  }
}
typescript
// main.ts
import { LogLayer } from "loglayer";

For detailed Deno setup and examples, see the Deno integration guide.

Bun ​

For Bun, you can install LogLayer using bun's package manager:

sh
bun add loglayer

For detailed Bun setup and examples, see the Bun integration guide.

Basic Usage with Structured Transport ​

The simplest way to get started is to use the built-in Structured Transport, which outputs structured log objects with level, time, and msg fields using the standard console object:

typescript
import { LogLayer, StructuredTransport } from 'loglayer'

const log = new LogLayer({
  transport: new StructuredTransport({
    logger: console,
  }),
  contextFieldName: 'context',
  metadataFieldName: 'metadata',
})

// Basic logging
log.info('Hello world!')
// { level: 'info', time: '2025-01-01T00:00:00.000Z', msg: 'Hello world!' }

// Logging with metadata
log.withMetadata({ user: 'john' }).info('User logged in')
// { level: 'info', time: '...', msg: 'User logged in', metadata: { user: 'john' } }

// Logging with context (persists across log calls)
log.withContext({ requestId: '123' })
log.info('Processing request')
// { level: 'info', time: '...', msg: 'Processing request', context: { requestId: '123' } }

// Logging errors
log.withError(new Error('Something went wrong')).error('Failed to process request')

Simple console logging

If you prefer unstructured console output, use the Console Transport instead.

Using an Error Serializer ​

When logging errors, JavaScript Error objects don't serialize to JSON well by default. We recommend using an error serializer like serialize-error to ensure error details are properly captured:

sh
npm install serialize-error
sh
pnpm add serialize-error
sh
yarn add serialize-error
typescript
import { LogLayer, StructuredTransport } from 'loglayer'
import { serializeError } from 'serialize-error'

const log = new LogLayer({
  errorSerializer: serializeError,
  transport: new StructuredTransport({
    logger: console,
  }),
})

// Error details will be properly serialized
log.withError(new Error('Something went wrong')).error('Failed to process request')

For more error handling options, see the Error Handling documentation.

Next steps ​