this small script intercepts the standard console methods and provides a way of accessing their messages, as well as stack traces, which is really cool. it formats the stack traces for popular browsers

custom_console.js

//==========================================================
// CUSTOM JAVASCRIPT CONSOLE
// built by jakub fiala
//
// this small script intercepts the standard console methods
// and provides a way of accessing their messages,
// as well as stack traces, which is really cool.
// it formats the stack traces for popular browsers
//
// contributions welcome!
//==========================================================


//taken from http://stackoverflow.com/a/21350614
//modified to get rid of the unused add variable
function str_splice(str, index, endIndex) {
  return str.slice(0, index)+str.slice(endIndex);
}

//taken from http://stackoverflow.com/a/7123542
//modified to make spans rather than anchors
if(!String.linkify) {
    String.prototype.linkify = function() {

        // http://, https://, ftp://
        var urlPattern = /\b(?:https?|ftp):\/\/[a-z0-9-+&@#\/%?=~_|!:,.;]*[a-z0-9-+&@#\/%=~_|]/gim;

        // www. sans http:// or https://
        var pseudoUrlPattern = /(^|[^\/])(www\.[\S]+(\b|$))/gim;

        // Email addresses
        var emailAddressPattern = /[\w.]+@[a-zA-Z_-]+?(?:\.[a-zA-Z]{2,6})+/gim;

        return this
            .replace(urlPattern, '<span class="link" data-href="$&">$&</span>')
            .replace(pseudoUrlPattern, '$1<span class="link" data-href="http://$2">$2</span>')
            .replace(emailAddressPattern, '<span class="link" data-href="mailto:$&">$&</span>');
    };
}

//taken from http://stackoverflow.com/a/7768006
//obviously isn't ideal but it's better than telling you to get Modernizr
//might add other browsers at some point, contributions are welcome!
var is_chrome = navigator.userAgent.toLowerCase().indexOf('chrome') > -1;
var is_firefox = navigator.userAgent.indexOf('Firefox') > -1;
var is_safari = navigator.userAgent.indexOf("Safari") > -1;


function stack_trace_format(stackTrace) {
  if (is_chrome) {
      //we first format the string a bit
      stackTrace = stackTrace.replace("Error","")
            .replace(/\r?\n|\r/g,'')
            .replace('    ','')
            .replace(/</gm,'&lt;')
            .replace(/>/gm,'&gt;');
      //then look for the first part of the trace (which is this method, we don't want that)
      for (var i = 0; i < stackTrace.length; i++) {
        if (stackTrace[i] == 'a' && stackTrace[i+1] == 't' && stackTrace[i+2] == ' ') {
          var startIndex = i;
          for (var j = startIndex+1; j < stackTrace.length; j++) {
            if (stackTrace[j] == 'a' && stackTrace[j+1] == 't' && stackTrace[j+2] == ' ') {
              var endIndex = j;
              //found beginning and end of this part, remove it
              stackTrace = str_splice(stackTrace,i,j);
              break;
            }
          }
          break;
        }
      }

      //then replace all 'at's with list elements, and convert to link spans
      stackTrace = stackTrace.replace(/at /gm,'</li><li>').linkify();
  }
  else if (is_safari || is_firefox) {
    //this seems to kind of work for both
    //turn spaces into list elmt boundaries, linkify, and replace at signs with html entities, just for the lulz
    stackTrace = '<li>' + stackTrace.replace(/\s/gm, '</li><li>').linkify().replace(/\@/gm,'&commat;');

    //again, look for the first part of the trace (which is this method, we don't want that)
    for (var i = 0; i < stackTrace.length; i++) {
      if (stackTrace[i] == '<' && stackTrace[i+1] == '/' && stackTrace[i+2] == 'l') {
        var index = i;
        //found end of this part, remove it
        stackTrace = str_splice(stackTrace,0,index);

        break;
      }
    }
  }

  return stackTrace;
}

//this is where everything happens
//basic code taken from http://tobyho.com/2012/07/27/taking-over-console-log/
(function custom_console_with_traces(){
    var console = window.console
    if (!console) return
    function intercept(method){
        var original = console[method]
        console[method] = function(){
            var message = Array.prototype.slice.apply(arguments).join(' ')
            //create an Error and get its stack trace and format it
            var stackTrace = stack_trace_format(new Error().stack);

            //==========================================================
            //do whatever you want with the stack trace and message here
            //==========================================================





            //==========================================================
            //make sure we still call the original method
            original.call(console, message)
        }
    }
    //intercept all methods including trace
    var methods = ['log', 'warn', 'error', 'trace']
    for (var i = 0; i < methods.length; i++)
        intercept(methods[i])
})();

Pretty neat, thanks for sharing!

This is not working in Chrome?? It is not firing when normal events are logged even though I run this code at the very start of page load.