CRUMB

A logging library focused on providing an easy to read logging output.

Usage

Before you can start logging anything, a new Logger object will need to be created.

Usually, it is good practice to instantiate a new Logger for each

import { Logger } from "https://deno.land/x/crumb/mod.ts";

const logger = new Logger("example_logger");

logger.debug("debug message");
logger.info("info message");
logger.warn("warn message");
logger.error("error message");

Please refer to the examples directory for more examples on how to use the CRUMB library.

Configuration

All configuration changes to the Logger can be configured via the LoggerConfig.setUp() method.

Application Name

The application name is first piece of data that is displayed within a log. This can be used to easily identify what application the log refers to if multiple applications are writing to the same log file.

Exmaple

import { LoggerConfig } from "https://deno.land/x/crumb/mod.ts";

LoggerConfig.setUp({
    appName: "application-name",
});

Log Level

Logging output can be configured to only log messages that meet a certain log level threshold. For example, if the log level is set to WARN, then only logs which greater or equal to the WARN log level will be logged (i.e. WARN and ERROR logs).

By default, the log level is set to INFO. This means that only INFO, WARN, and ERROR logs will be logged.

Below shows how different log levels compare with each other:

DEBUG < INFO < WARN < ERROR

Example

import { LoggerConfig, LogLevel } from "https://deno.land/x/crumb/mod.ts";

LoggerConfig.setUp({
    level: LogLevel.ERROR,
});

Handlers

A handler is responsible for handling all of the log messages. There are two types of handlers:

1. ConsoleHandler
2. FileHandler

A ConsoleHandler is responsible for logging all of the log messages to the standard output (i.e. the console). While the FileHandler is responsible for logging all of the log messages to a specified file.

You can have an many handlers as you want. This could be useful in situations where you want to have a file consiting all all logs (i.e. logs.txt) and also a file consisting of only errors (i.e. errors.txt).

By default, there is only a single ConsoleHandler.

Example

import { FileHandler, LoggerConfig } from "https://deno.land/x/crumb/mod.ts";

LoggerConfig.setUp({
    handlers: [
        new FileHandler("./logs.txt"),
    ],
});

This is an example of configurting the logger to output all logs to a logs.txt file in the root directory.

Interceptors

An interceptor is a function which is executed before any logging occurs (i.e. outputted to the console or written to a file).

This can be useful in situations where you want certain actions to be performed on every log (i.e. writing to a log management platform).

Example

import { LoggerConfig, LogLevel } from "https://deno.land/x/crumb/mod.ts";

LoggerConfig.setUp({
    interceptors: [
        (msg: string, logLevel: LogLevel, loggerName: string) => {
            // do something
        },
    ],
});

This is an example of configurting the logger with a single interceptor function. An interceptor function provides three arguments which can be used within the function, the message which is logged, the log level (i.e. DEBUG, INFO, WARN, ERROR), and the logger name.

License

Apache License 2.0