Introduction

Simple Javascript Logger

❓ logger

The logger package is a standalone extension for AgileTs that improves the logging experience, by letting you precisely configure the logging behavior of AgileTs packages. Without the logger package installed, AgileTs only logs warn and error log messages. These logs cannot be customized or turned off. However, with the logger extension installed, you can completely customize what messages should be logged, how these messages should look like and much more. All you need to do to configure the logging behavior of AgileTs, is to call assignSharedLogger() and specify your customized logger configuration.

import {assignSharedLogger, createLogger, Logger} from '@agile-ts/logger';

assignSharedLogger(createLogger({
  active: true,
  level: Logger.level.DEBUG,
  timestamp: true
}));

✍️ Standalone

The AgileTs Logger Class can also be used without AgileTs installed.

const logger = new Logger();

Some of its basic capabilities are to:

• 🎭 categorize log messages

  Log messages in different upper categories to be able to roughly classify log messages.

  logger.log("I'm a log message!");
  logger.debug("I'm a debug message!");
  logger.info("I'm a info message!");
  logger.warn("I'm a warn message!");
  logger.error("I'm a error message!");
  logger.success("I'm a success message!");
  logger.trace("I'm a trace message!");
  logger.custom('jeff', "I'm a custom jeff message!");

• 🎲 filter log messages

  Filter log messages by tag or type in order to see only logs that matter right now.

  // Filter by 'type'
  logger.setLevel(Logger.level.WARN);
  logger.debug('Boring Debug Message.'); // Doesn't get logged
  logger.warn('Important Warning!'); // Does get log
  
  // Filter by 'tags'
  logger.if.tag(['runtime']).info(`Created Job '${job._key}'`, job);

• 🎨 style log messages (color, font-weight)

  Style log messages to make it easier to distinguish between different log types and recognise important log messages more quickly.

• 🔨 customize log messages (prefix, timestamp)

  Customize log messages to identify searched logs more swiftly.

  logger.debug('Hello there!'); // Logs: 'Agile: Hello there!'

• 🚫 disable all log messages

  logger.debug('Exciting Debug Message.'); // Logs: 'Boring Debug Message.'
  logger.isActive = false;
  logger.debug('Boring Debug Message.'); // Doesn't get logged
  logger.warn('Important Warning!'); // Doesn't get logged

📭 Props

// Stand alone Logger
new Logger(config);

// AgileTs Logger
assignSharedAgileLoggerConfig(config);

config

The Logger Class takes an optional configuration object as its only parameter.

new Agile({
  active: true,
  level: Logger.level.DEBUG,
  timestamp: true
});

Here is a Typescript Interface for quick reference. However, each property is explained in more detail below.

export interface CreateLoggerConfigInterface {
  prefix?: string;
  allowedTags?: LoggerKey[];
  canUseCustomStyles?: boolean;
  active?: boolean;
  level?: number;
  timestamp?: boolean;
}

prefix

Prefix which is added before each log message.

const logger = new Logger({
    prefix: "MyLog"
});

logger.debug("Jeff"); // Logs 'MyLog Debug: Jeff'

The log messages of AgileTs have the default prefix "Agile".

Type	Default	Required
string	"Agile"	No

level

The log level controls which kind of log messages are allowed to be logged. Therefore, it is used to filter log messages to only see these relevant to us. For example, we won't often set the log level to debug since debug messages flood the console and are, in most cases, not relevant for us.

const logger = new Logger({
    level: Logger.level.WARN
});

logger.debug("Jeff"); // Doesn't get logged
logger.warn("A important Warning"); // Gets logged

The Logger Class supports some hard-coded log levels, which can be set dynamically.

{
    TRACE: 1,
    DEBUG: 2,
    LOG: 5,
    TABLE: 5,
    INFO: 10,
    SUCCESS: 15,
    WARN: 20,
    ERROR: 50,
}

Logger.level.LOG; // 5

For example, suppose we set the logger level to INFO. In that case, each log category at a higher or same level is printed to the console. In the case of INFO, that would be SUCCESS, WARN, ERROR and of course INFO.

Type	Default	Required
number	20	No

active

Determines whether the logger is active and is allowed to print messages to the console.

const logger = new Logger({
    active: false
});

logger.log("Jeff"); // Doesn't get logged
logger.isActive = true;
logger.log("Jeff"); // Gets logged

Type	Default	Required
boolean	true	No

timestamp

If true, a timestamp is added before each log message. This timestamp represents the time the message was logged.

const logger = new Logger({
    timestamp: true
});

logger.debug("Jeff"); // Logs '[1613108673781] Debug: Jeff'

Type	Default	Required
boolean	false	No

allowedTags

Sometimes logging can be very confusing and overwhelming if the console is flooded with logs that don't matter at the time. Therefore, tags got created which filter logs specifically by tags.

const logger = new Logger({
    allowedTags: ["jeff", "hans"]
});

logger.debug("Jeff"); // Gets logged
logger.if.tag(["jeff"]).debug("Jeff"); // Doesn't get logged
logger.if.tag(["hans", "jeff"]).debug("Jeff");; // Gets get logged
logger.if.tag(["hans"]).debug("Jeff");; // Doesn't get logged
logger.if.tag(["hans", "frank"]).debug("Jeff");; // Doesn't get logged

Any log message with defined tags will only be logged if all its tags are allowed in the Logger Class. Logs that have no condition/tag are always logged.

Type	Default	Required
string[]	['runtime', 'storage', 'subscription', 'multieditor']	No

canUseCustomStyles

Whether we can apply custom css styles to the log messages.

For example, AgileTs Logs are by default purple.

Type	Default	Required
boolean	true	No

🟦 Typescript

The Logger is almost 100% typesafe.

🚀 Quick Links

• Installation