Solution: loglevel is a JavaScript logging library that is reliable and extremely easy-to-use over the various console.log() methods. loglevel is a lightweight, minimal and convenient JavaScript logging library which provides a reliable and extremely easy-to-use layer over the various console.log() methods that are often available, with none of their downsides.

Solution:  loglevel is a lightweight, minimal and convenient JavaScript logging library which provides a reliable and extremely easy-to-use layer over the various console.log() methods that are often available, with none of their downsides. loglevel makes these methods safe to use by gracefully handling the cases where they don’t exist and also lets you filter the output of these, to only show messages at warn level or above.

Solution: Apache Log4j is a Java-based logging utility. It was originally written by Ceki Gülcü and is part of the Apache Logging Services project of the Apache Software Foundation. Since a major use of JavaScript logging is in browser testing, log4javascript is tested and works across all recent major browsers, including:
Internet Explorer 5+ for Windows
Mozilla, Firefox, Netscape
Google Chrome
Safari 1.3+
Opera 7.5+
WebKit
Konqueror 3.4+

Solution: Apache Log4j is a Java-based logging utility.log4javascript is a fully-featured, easy-to-use JavaScript logging framework based on the Java logging framework log4j. Its purpose is to provide JavaScript developers with a familiar, robust and flexible logging framework with which to debug JavaScript applications.

Solution: Lumberjack is a JavaScript utility that hijacks the browser console, makes it more beautiful and enhances it so logs can be split into more manageable chunks. Lumberjack also saves everything that is logged (so you can review later) and colorizes your logs (where supported) to increase legibility.

Solution: jsTracer is a simple yet feature rich JavaScript logging and debugging tool. It is especially useful for debugging what has been coined “Web 2.0” code. It helps in dynamic tracing for JavaScript, written in JavaScript, providing you insight into your live nodejs applications, at the process, machine, or cluster level.

Solution: Log Hound is a tool that was designed for finding frequent patterns from event log data sets with the help of a breadth-first frequent itemset mining algorithm. LogHound can be employed for mining frequent line patterns from raw event logs, e.g. Log Hound is a standalone JavaScript logging utility that allows you to log messages during execution of JavaScript code.

Solution: There are several ways to log using “appender”s. Some of the current available Appenders are:
DummyAppender: log nothing.
ConsoleAppender: open a new window in the browser or an inline div element and insert log messages in real time.
WindowsEventAppender: send log messages in the MS Windows event manager (Internet Explorer only).
FileAppender: write log messages in a local file on the client (IE and Mozilla).
AjaxAppender: allow to send log messages to a remote server with asynchronous HTTP request.
MetatagAppender: add log messages as meta data.
JavaScript Console Appenders for Opera, Mozilla and Safari.

Solution: readUrl() opens an input connection to the given string url, read all its bytes and convert them to a string using the specified character coding or default character coding if an explicit coding argument is not given.

Solution: If you use .Net, JSNLog has server side extensions that receive log data from the browser and have it logged on the server. And it lets you configure your loggers in your web.config. It includes a large class library named as Framework Class Library and provides language interoperability across several programming languages.