Simplr Logger

Simple JavaScript logger written in TypeScript that can be used in browser or node application.

The package is most useful when used with TypeScript.

Get started

npm install simplr-logger

Building logger

With default configuration

import { LoggerBuilder } from "simplr-logger";

const logger = new LoggerBuilder();

With configuration builder

import { LoggerBuilder, LoggerConfigurationBuilder, LogLevel } from "simplr-logger";
import { FileMessageHandler, ConsoleMessageHandler } from "simplr-logger/handlers";

const config = new LoggerConfigurationBuilder()
    .SetDefaultLogLevel(LogLevel.Trace)
    .AddWriteMessageHandlers([
        { Handler: new ConsoleMessageHandler() },
        { Handler: new FileMessageHandler("./logs.txt") }]
    )
    .Build();

const logger = new LoggerBuilder(config);

With simple object

import { LoggerBuilder, LogLevel, ConsoleMessageHandler } from "simplr-logger";

const logger = new LoggerBuilder({
    DefaultLogLevel: {
        LogLevel: LogLevel.Trace,
        LogLevelIsBitMask: false
    },
    WriteMessageHandlers: [{
        Handler: new ConsoleMessageHandler(),
        LogLevel: LogLevel.Critical | LogLevel.Debug,
        LogLevelIsBitMask: true
    }]
});

Creating logger handler

import { MessageHandlerBase, LogLevel, LoggerBuilder, LoggerConfigurationBuilder } from "simplr-logger";

class MyMessageHandler extends MessageHandlerBase {
    public HandleMessage(level: LogLevel, timestamp: number, messages: any[]): void {
        console.log(...messages);
    }
}

const config = new LoggerConfigurationBuilder()
    .AddWriteMessageHandler({ Handler: new MyMessageHandler(), LogLevel: LogLevel.Trace })
    .Build();

const logger = new LoggerBuilder(config);

Using logger

Logging with methods

logger.Critical("Critical", "message");
logger.Debug("Debug", "message");
logger.Error("Error", "message");
logger.Info("Info", "message");
logger.Warn("Warn", "message");
logger.Trace("message", "with trace");

Logging with log level

logger.Log(LogLevel.Information, "Info message");
logger.Log(LogLevel.Critical, new Error("Critical error"));

Updating configuration

// Using old configuration
logger.UpdateConfiguration(builder => builder.SetPrefix("[new prefix]").Build());

// Or with default configuration
logger.UpdateConfiguration(builder => builder.SetPrefix("[new prefix]").Build(), false);

API

LogLevel

Name	Value	Description
None	0	Not used for writing log messages. Specifies that logger should not write any messages.
Critical	1	Logs that describe an unrecoverable application or system crash, or a catastrophic failure that requires immediate attention.
Error	2	Logs that highlight when the current flow of execution is stopped due to a failure. These should indicate a failure in the current activity, not an application-wide failure.
Warning	4	Logs that highlight an abnormal or unexpected event in the application flow, but do not otherwise cause the application execution to stop.
Information	8	Logs that track the general flow of the application. These logs should have long-term value.
Debug	16	Logs that are used for interactive investigation during development. These logs should primarily contain information useful for debugging and have no long-term value.
Trace	32	Logs that contain the most detailed messages. These messages may contain sensitive application data. These messages are disabled by default and should never be enabled in a production environment.

Configuration

Name	Default value	Description
WriteMessageHandlers	`[{ Handler: new ConsoleMessageHandler() }]`	Message handlers list. ⁽¹⁾
DefaultLogLevel	`{ LogLevel: LogLevel.Warning, LogLevelIsBitMask: false }`	Log level or log levels in bit mask value.
Prefix	`undefined`	Custom message, which will be injected into the start of messages.

(1) - The default value is only available if configuration property is not set.

License

Released under the MIT license.

SimplrJS/simplr-logger