'console' is undefined error for Internet Explorer
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?
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.
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.
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.
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