# glogg
A simple, structured JSON logging library for Gleam that works across Erlang and JavaScript targets.
*Named after the traditional Scandinavian mulled wine that warms you up during cold winter nights, this logging library aims to bring the same cozy, warming comfort to your debugging sessions.*
[](https://hex.pm/packages/glogg)
[](https://hexdocs.pm/glogg/)
## Features
- **Structured JSON Logging** - Clean, parseable log output
- **Type-Safe Fields** - String, Int, Float, Bool, and nested Group fields
- **Flexible Configuration** - Custom writers, default fields, and minimum levels
- **Cross-Platform** - Works on both Erlang and JavaScript targets
## Quick Start
```sh
gleam add glogg
```
```gleam
import glogg.{bool, info, int, string}
pub fn main() {
let logger = glogg.new()
info(logger, "This is fine", [
bool("everything_burning", True),
string("glogg_temperature", "still_hot"),
int("production_issues", 42069)
])
}
```
**Output:**
```json
{"time":"2025-09-25T22:03:45.124Z","level":"INFO","msg":"This is fine","everything_burning":true,"glogg_temperature":"still_hot","production_issues":42069}
```
## Usage Examples
### Structured Fields
```gleam
info(logger, "Processing payment", [
string("payment_id", "pay_123"),
float("amount", 29.99),
int("user_id", 12345),
bool("verified", True)
])
```
### Nested Fields
```gleam
info(logger, "API request completed", [
group("request", [
string("method", "POST"),
string("path", "/api/users"),
int("status", 201)
]),
group("response", [
float("duration_ms", 45.2),
int("bytes", 1024)
])
])
```
### Logger Configuration
```gleam
// Set minimum log level
let logger =
glogg.new()
|> with_min_level(Info)
// Only Info, Warn, Error
// Add default fields to all logs
let logger =
glogg.new()
|> with_default_fields([
string("service", "web-api"),
string("version", "1.2.3"),
])
// Add more default fields later
let logger =
logger
|> add_default_fields([string("environment", "production")])
```
### Custom Writers
```gleam
// Custom writer function
let file_writer = fn(line: String) {
// Write to file, send to external service, etc.
io.println("LOG: " <> line)
}
let logger =
glogg.new()
|> with_writer(file_writer)
|> with_error_writer(file_writer) // Separate error writer
```
