# slf4ts-api Simple Logging Facade for NodeJS

Inspired by the popular Java lib [SLF4J](https://www.slf4j.org) This project is used to abstract logging to develop reusable libraries and not force the usage of a certain logging framework. It's meant to be used with `nodejs`. ## LogLevel * TRACE (numeric value: `4`) * DEBUG (numeric value: `3`) * INFO (numeric value: `2`) * WARN (numeric value: `1`) * ERROR (numeric value: `0`) ## Logger Implementations slf4ts doesn't work without a logging-framework binding. Bindings exist for a couple of logging-frameworks: * [console](../slf4ts-console) * [log4js](../slf4ts-log4js) * [winston](../slf4ts-winston) ### Write a binding A binding for a logging-framework needs to implement the `LoggerBinding` interface and the actual logger interface `LoggerImplementation`. Also a file named `.slf4ts-binding` needs to be present in the package folder (can be empty). A node package for a binding should export a single function that is used during binding discovery. Interfaces to implement: ```typescript import { LogLevel } from "slf4ts-api"; interface LoggerImplementation { log(...args: any[]): Promise; getImplementation(): T; setConfig(config: T, group: string, name: string): void; setLogLevel(logLevel: LogLevel, group: string, name: string): void; setMetadata(metadata: any, group: string, name: string): void; } interface LoggerBinding { getLoggerImplementation(): LoggerImplementation; getVendor(): string; getVersion(): string; } ``` Sample implementation in typescript (index.ts): ```typescript import { LoggerBindings } from "slf4ts-api"; export default function(bindings: LoggerBindings) { bindings.registerBinding({ getLoggerImplementation: () => { ... }, getVendor: () => "My Logger Binding Implementation", getVersion: () => "1.0.0" }); } ``` An example implementation can be found in the `example-node-modules` folder of this project. ## Usage ```typescript import { LoggerConfiguration, LogLevel, LoggerFactory } from "slf4ts-api"; // gets the root logger (group "" and name "") const ROOT_LOGGER = LoggerFactory.getLogger(); class X { // gets a logger with group "my-lib" and name "X" private static LOG = LoggerFactory.getLogger("my-lib", "X"); public async something(value: any) { // log with debug level and some metadata X.LOG.debug(`a message with ${value}`, { additionalData: "Testvalue" }); try { ... } catch(error: Error) { // logs an error without metadata X.LOG.error('Error!', error); } } } // sets the log level of all loggers LoggerConfiguration.setLogLevel(LogLevel.INFO); // sets the log level of all loggers within group "my-lib" LoggerConfiguration.setLogLevel(LogLevel.WARN, "my-lib"); // sets the log level of the logger with group "my-lib" and name "X" LoggerConfiguration.setLogLevel(LogLevel.ERROR, "my-lib", "X"); const config = { transports: [...], events: [...], postProcessor: () => { ... } }; // sets the config of all loggers LoggerConfiguration.setConfig(config); // sets the config of all loggers within group "my-lib" LoggerConfiguration.setConfig(config, "my-lib"); // sets the config of the logger with group "my-lib" and name "X" LoggerConfiguration.setConfig(config, "my-lib", "X"); ``` ## License [MIT](https://www.opensource.org/licenses/mit-license.php)