loglevel-local-storage

NPM plugin for JS logger loglevel which will log all messages to localStorage

Features

• Messages put on a stack, stack is stored entirely.
• Max stack size for logs to be stored can be set.
• You can specify prefix function which would dynamically add prefix for all log messages (app name, current user, etc.).

Installation

• Using npm = npm install loglevel-local-storage

Configuration

import loglevel and loglevel-localStorage scripts to your file first. Then configure the plugin:

loglevelLocalStorage(logger, options)

Extend loglevel with new plugin which will send log information to the log-sever

Param	Type	Description
logger	object	loglevel instance to be extended
options	object
[options.storeKey='loglevelLocalStorage']	string	Name for the store in localStorage.
[options.maxLogStackSize=100]	number	Max stack size to store.
[options.callOriginal=false]	Bool	If set to true - original loglevel method for logging would be called
[options.prefix=null]	string | function	Prefix for all log messages. Either string or function wich should return string and accept log severity and message as parameters
[options.level=logger.levels.WARN]	string | number	Log level. Either string or number, See loglevel.setLevel.
[options.persistentLog=false]	Bool	If set to true - persist log entries between instantiations of the same log stack.

Example

                                                
var debuglog = require('loglevel'); // import debuglog from 'loglevel';
var loglevelLocalStorage = require('../loglevel-localStorage.js'); // import loglevelLocalStorage from 'loglevel-local-storage';
 
debuglog.setLevel(1);
 
loglevelLocalStorage(debuglog, {
    level: 'info',
    prefix: function (logSev /* , ...message */) {
        var message = Array.prototype.slice.call(arguments, 1);
        return '[' + new Date().toISOString() + '] ' + logSev + ': ' + message.join(' ');
    },
    callOriginal: true,
    maxLogStackSize: 10
});
 
var foo = function () {
    var test = "123";
    debuglog.info("test", test);
};
 
foo();
 
// output console (callOriginal = true):  
// test 123
// output localStorage (see prefix function above):
// [2016-07-19T15:39:18.110Z] info: test 123
 
// ES6 example:
import debuglog from 'loglevel';
import loglevelLocalStorage from 'loglevel-local-storage';
 
debuglog.setLevel("DEBUG");
loglevelLocalStorage(debuglog, {
    level: 'info',
    prefix(logSev, ...args) {
        // Stringify for storage in localStorage
        const newArgs = args.map(arg => ((typeof arg === 'object' && !(arg instanceof Date)) ? JSON.stringify(arg) : arg));
        return `[${new Date().toISOString()}] ${logSev}: ${newArgs.join(' ')}`;
    },
    callOriginal: true,
    maxLogStackSize: 10,
});
 

Another Prefix Example

You may keep the log in a JSON format to be able to parse later

    ...
    prefix: function (logLevel) {
        var message = Array.prototype.slice.call(arguments, 1);
        return [new Date(), logLevel, message];
    }
    ...