// Tell IE9 to use its built-in console
if (Function.prototype.bind && (typeof console === 'object' || typeof console === 'function') && typeof console.log == "object") {
  ["log","info","warn","error","assert","dir","clear","profile","profileEnd"]
    .forEach(function (method) {
      console[method] = this.call(console[method], console);
    }, Function.prototype.bind);
}

// log() -- The complete, cross-browser (we don't judge!) console.log wrapper for his or her logging pleasure
if (!window.log) {
  window.log = function () {
    log.history = log.history || [];  // store logs to an array for reference
    log.history.push(arguments);
    // Modern browsers
    if (typeof console != 'undefined' && typeof console.log == 'function') {

      // Opera 11
      if (window.opera) {
        var i = 0;
        while (i < arguments.length) {
          console.log("Item " + (i+1) + ": " + arguments[i]);
          i++;
        }
      }

      // All other modern browsers
      else if ((Array.prototype.slice.call(arguments)).length == 1 && typeof Array.prototype.slice.call(arguments)[0] == 'string') {
        console.log( (Array.prototype.slice.call(arguments)).toString() );
      }
      else {
        console.log( Array.prototype.slice.call(arguments) );
      }

    }

    // IE8
    else if (!Function.prototype.bind && typeof console != 'undefined' && typeof console.log == 'object') {
      Function.prototype.call.call(console.log, console, Array.prototype.slice.call(arguments));
    }

    // IE7 and lower, and other old browsers
    else {
      // Inject Firebug lite
      if (!document.getElementById('firebug-lite')) {
        // Include the script
        var script = document.createElement('script');
        script.type = "text/javascript";
        script.id = 'firebug-lite';
        // If you run the script locally, point to /path/to/firebug-lite/build/firebug-lite.js
        script.src = 'https://getfirebug.com/firebug-lite.js';
        // If you want to expand the console window by default, uncomment this line
        //document.getElementsByTagName('HTML')[0].setAttribute('debug','true');
        document.getElementsByTagName('HEAD')[0].appendChild(script);
        setTimeout(function () { log( Array.prototype.slice.call(arguments) ); }, 2000);
      }
      else {
        // FBL was included but it hasn't finished loading yet, so try again momentarily
        setTimeout(function () { log( Array.prototype.slice.call(arguments) ); }, 500);
      }
    }
  };
}

http://patik.com/blog/complete-cross-browser-console-log/

For those who refuse to upgrade.

Console Log Cross-browser Compatibility

JavaScript