Requirements

This library will work with any typescript project such as:

• nodeJS + typescript
• Angular2 + typescript

Description

I saw in many projects developers who use console.log, console.warn, etc.. everywhere in their code. Then, they want to push their code to production servers. But oh!! The logs! They are spreaded everywhere in the code and they are useful. Using a new logger library to replace all these logs can be painful and somewhat cumbersome. So why not just wrapping all console by a logger, that would let the code untouched ? Well, this is exactly what this library does! :)

This library is a wrapper around console that allow to show the proper level of logs in the code without touching the console.x occurrences in your code and without having to write a logger and inject it in all functions that need some logging. Instantiate this code once will allow you to set the log level without touching your console.X methods in your code.

It keeps the line number of the original log.

Log level

The following rules is applied:

TRACE < DEBUG < INFO < WARN < ERROR

So setting the log level to "trace" will show all the detailed logs. But obviously, in production, you probably prefer to only show a "warn" or "error" level.

In a more graphic way, here is how the selection rule works. In the following table, the vertical header shows the level of the logging request, designated by p, while the horizontal header shows effective level of the logger, designated by q. The intersection of the rows (level request) and columns (effective level) is the boolean resulting from the basic selection rule.

How to use

At the beginning of your program, call the following:

import { Logger } from 'console-logger'
new Logger({ level: 'trace' })

Available console methods

The following methods are wrapped:

• trace
• debug
• info
• warn
• error
• dir
• log

Options

• level: log level
• callback: a function to execute before the log is output. It won't be executed if the log level is not high enough
• forceCallback: force the callback to be executed even if the log level does not allow it

Examples

Basic logger with log filtering

Suppose you're in prod, you may want to disable all logs:

import { Logger } from 'console-logger'
new Logger({ level: 'off' })

Run additional logic when console methods are called

import { Logger } from 'console-logger'
const options = {
   level: 'off',
   info: {
       callback: function(){
	       // so something here
	   }
   },
   error: {
       callback: function(){
	       reportToCloud('blah', arguments); // send error to remote server
	   },
       forceCallback: true
   }
}
window.logger = new Logger(options)

Reload options

You can reload the logger without re-instantiating it:

logger = window.logger
logger.options.log.callback = function() {
    // do something
}
logger.reloadOptions()

Build

Run:

tsc index.ts

to generate index.js