Log Levels

Level hierarchy

log-wiz supports seven levels in ascending severity order:

Level	Severity	Badge	When to use
trace	10	TRACE	Step-by-step debugging, very high volume
debug	20	DEBUG	Development diagnostics
info	30	INFO	Normal operational events
warn	40	WARN	Unexpected but recoverable
error	50	ERROR	An operation failed
fatal	60	FATAL	Process-level failure
none	Inf	—	Silence all output (no-op mode)

---

Filtering

Setting a level on your logger drops all entries below that severity:

import { Wiz } from "@gouranga_samrat/log-wiz";

const logger = new Wiz({ level: "warn" });

logger.trace("ignored");  // severity 10 < 40 -> dropped
logger.debug("ignored");  // severity 20 < 40 -> dropped
logger.info("ignored");   // severity 30 < 40 -> dropped
logger.warn("logged [ok]");  // severity 40 = 40 -> written
logger.error("logged [ok]"); // severity 50 > 40 -> written
logger.fatal("logged [ok]"); // severity 60 > 40 -> written

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Default level

The default level is info — trace and debug are dropped unless you explicitly lower it.

// Development: lower to debug to see more detail
const logger = new Wiz({ level: "debug" });

// Production: keep at info or higher
const logger = new Wiz({ level: "info" });

---

No-op mode

Set level: 'none' to completely silence the logger without removing any code. Every log call returns immediately — no string formatting, no masking, no I/O. True zero overhead.

const logger = new Wiz({
  level: process.env.NODE_ENV === "test" ? "none" : "info",
});

Tip

No-op mode is the correct way to silence logs in tests. Unlike mocking console, it doesn’t require any setup/teardown and adds zero overhead.

---

Runtime level change

Use setConfig() to change the level without creating a new instance:

const logger = new Wiz({ level: "info" });

// Increase verbosity on demand (e.g. triggered by a signal or feature flag)
process.on("SIGUSR1", () => {
  logger.setConfig({ level: "debug" });
  logger.info("Log level changed to debug");
});

// Silence during shutdown
process.on("SIGTERM", async () => {
  logger.setConfig({ level: "none" });
  await logger.close();
  process.exit(0);
});

---

Level in TypeScript

The LogLevel type is exported for use in your own code:

import type { LogLevel } from "@gouranga_samrat/log-wiz";
import { LOG_LEVEL_SEVERITY } from "@gouranga_samrat/log-wiz";

function isAtLeast(entry: LogLevel, threshold: LogLevel): boolean {
  return LOG_LEVEL_SEVERITY[entry] >= LOG_LEVEL_SEVERITY[threshold];
}

isAtLeast("error", "warn");  // true
isAtLeast("debug", "info");  // false