'console' is undefined error for Internet Explorer

04/26/2020 09:00:01

I'm using Firebug and have some statements like:

console.log("...");

in my page. In IE8 (probably earlier versions too) I get script errors saying 'console' is undefined. I tried putting this at the top of my page:

<script type="text/javascript">
    if (!console) console = {log: function() {}};
</script>

still I get the errors. Any way to get rid of the errors?

Verified Answer (378 Votes)

07/25/2010 00:57:33

Try

if (!window.console) console = ...

An undefined variable cannot be referred directly. However, all global variables are attributes of the same name of the global context (window in case of browsers), and accessing an undefined attribute is fine.

Or use if (typeof console === 'undefined') console = ... if you want to avoid the magic variable window, see @Tim Down's answer.

378

Answer #2 (317 Votes)

12/11/2012 14:28:45

Paste the following at the top of your JavaScript (before using the console):

/**
 * Protect window.console method calls, e.g. console is not defined on IE
 * unless dev tools are open, and IE doesn't define console.debug
 * 
 * Chrome 41.0.2272.118: debug,error,info,log,warn,dir,dirxml,table,trace,assert,count,markTimeline,profile,profileEnd,time,timeEnd,timeStamp,timeline,timelineEnd,group,groupCollapsed,groupEnd,clear
 * Firefox 37.0.1: log,info,warn,error,exception,debug,table,trace,dir,group,groupCollapsed,groupEnd,time,timeEnd,profile,profileEnd,assert,count
 * Internet Explorer 11: select,log,info,warn,error,debug,assert,time,timeEnd,timeStamp,group,groupCollapsed,groupEnd,trace,clear,dir,dirxml,count,countReset,cd
 * Safari 6.2.4: debug,error,log,info,warn,clear,dir,dirxml,table,trace,assert,count,profile,profileEnd,time,timeEnd,timeStamp,group,groupCollapsed,groupEnd
 * Opera 28.0.1750.48: debug,error,info,log,warn,dir,dirxml,table,trace,assert,count,markTimeline,profile,profileEnd,time,timeEnd,timeStamp,timeline,timelineEnd,group,groupCollapsed,groupEnd,clear
 */
(function() {
  // Union of Chrome, Firefox, IE, Opera, and Safari console methods
  var methods = ["assert", "cd", "clear", "count", "countReset",
    "debug", "dir", "dirxml", "error", "exception", "group", "groupCollapsed",
    "groupEnd", "info", "log", "markTimeline", "profile", "profileEnd",
    "select", "table", "time", "timeEnd", "timeStamp", "timeline",
    "timelineEnd", "trace", "warn"];
  var length = methods.length;
  var console = (window.console = window.console || {});
  var method;
  var noop = function() {};
  while (length--) {
    method = methods[length];
    // define undefined methods as noops to prevent errors
    if (!console[method])
      console[method] = noop;
  }
})();

The function closure wrapper is to scope the variables as to not define any variables. This guards against both undefined console and undefined console.debug (and other missing methods).

EDIT: I noticed that HTML5 Boilerplate uses similar code in its js/plugins.js file, if you're looking for a solution that will (probably) be kept up-to-date.

317

Answer #3 (73 Votes)

07/25/2010 01:09:38

Another alternative is the typeof operator:

if (typeof console == "undefined") {
    this.console = {log: function() {}};
}

Yet another alternative is to use a logging library, such as my own log4javascript.

73
3
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