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I would like to extend the 'console.log' function to add additional information to its output - but I dont want to affect the script name/line number information generated by the browser in the console window. See how if I create my own implementation, I get useless trace information, should I want to locate that region of code... (they all link to the log implementation, not the actual script that caused the log message)
Basically, my application is a very pluggable infrastructure, were any log output may occur within any number of frames. As such, I want every log message to include a special unique identifier at the beginning of the log message.
I have tried replacing the console.log method with my own, but chrome complains with Uncaught TypeError: Illegal invocation
this is how I override it
var orig = console.log; console.log = function( message ) { orig( (window == top ? '[root]' : '[' + window.name + ']') + ': ' + message ); } Any ideas?
[EDIT] Note: After fixing the 'illegal invocation' problem, it seems the filename/linenumber is still 'polluted' by the override...
[EDIT] It looks like the general answer is - NO - despite some confusing goose chases, the desired functionality is NOT achievable in the current versions of browsers.
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To create a multi line strings when printing to the JavaScript console, you need to add the new line character represented by the \n symbol. Alternatively, you can also add a new line break using Enter when you use the template literals syntax.
console. log by itself doesn't really impact performance in a way that you'll notice unless you bind it to a scroll / resize handler. These get called alot and if your browser has to send text to the console like 30/60x a second it can get ugly.
As said above, the console. log is asynchronous and non-blocking, so it would not slow your application too much except one tick for the function invocation. But it is a good habit to use some module to turn some logs of certain level off when deploy it in production instead of using console.
Yes, it is possible to add information without messing up the originating line numbers of the log invocation. Some of the other answers here came close, but the trick is to have your custom logging method return the modified logger. Below is a simple example that was only moderately tested that uses the context variant.
log = function() { var context = "My Descriptive Logger Prefix:"; return Function.prototype.bind.call(console.log, console, context); }(); This can be used with:
log("A log message..."); Here is a jsfiddle: http://jsfiddle.net/qprro98v/
One could get easily get creative and pass the context variable in, and remove the auto-executing parens from the function definition. i.e. log("DEBUG:")("A debug message"), log("INFO:")("Here is some info"), etc.
The only really import part about the function (in regards to line numbers) is that it returns the logger.
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