@aglyn/shared-util-logger

A small leveled logger: named instances, a log level per instance, and a replaceable handler. The larger Aglyn packages log through it, and it works on its own. Its shape follows @firebase/logger; it depends on nothing.

Beta. Published from the Aglyn monorepo under the beta dist-tag; APIs can change between beta releases.

Install

npm install @aglyn/shared-util-logger@beta

Usage

Create one Logger per component, named for it:

import { Logger, LogLevel } from '@aglyn/shared-util-logger'

const logger = new Logger('@acme/checkout')
logger.setLogLevel(LogLevel.WARN)
logger.warn('inventory is stale', { sku })

logLevel decides which calls reach the handler. logHandler replaces the default handler, which writes to the console, and userLogHandler adds one that runs beside it, for forwarding logs somewhere else.

Each Logger instance supports 5 log functions each to be used in a specific instance:

• debug: Internal detail, for diagnosing an issue.
• log: Use to inform your user about things they may need to know.
• info: Use if you have to inform the user about something that they need to take a concrete action on. Once they take that action, the log should go away.
• warn: Use when a product feature may stop functioning correctly; unexpected scenario.
• error: Only use when user App would stop functioning correctly - super rare!

Log Format

Each log will be formatted in the following manner:

`"[${new Date()}] ${COMPONENT_NAME}: ${...args}"`

License

Apache-2.0. Source: https://github.com/aglyn/aglyn/tree/main/libs/shared/util/logger