what is variable "external" meant for in javascript

Question

I just found out that there is a variable called external exists in most browsers except IE. I have 2 question wrt to this

what is external - http://jsfiddle.net/EVBjU/
IE gives object doesn't support this property or method when i do console.log(external). how to fix this, considering it's just a variable

Thanks

see http://stackoverflow.com/questions/10694341/what-is-the-use-of-window-external — Fabrizio Calderan, Jul 22 '13 at 10:30
What do you mean by "fix this"? Simply removing the logging statement will remove the error. — David Pärsson, Jul 22 '13 at 10:31
@DavidPärsson i know that but how do i fix a "object doesn't support this property or method" in general — aWebDeveloper, Jul 22 '13 at 10:32
There is no fix, since what you're doing is not supported. The only fix is to not do it. — David Pärsson, Jul 22 '13 at 10:35
@DavidPärsson is there a way to check if the variable external exists — aWebDeveloper, Jul 22 '13 at 10:35
@ShadowWizard - IE does have `console.log()`. It's just that in IE it gives an error unless the console is already open (and actually I think MS fixed that in IE10). — nnnnnn, Jul 22 '13 at 10:40
@nnnn it never worked for me, however will delete the comment to avoid confusing people. — Shadow The GPT Wizard, Jul 22 '13 at 10:45
@WebDeveloper using IE is bad. Period. It will always lag behind the real browsers. Luckily enough, people understand that and its usage is ever decreasing. — Shadow The GPT Wizard, Jul 22 '13 at 10:45
@ShadowWizard http://www.netmarketshare.com/.... IE is way above others(they include china and other asian non-english data ) — aWebDeveloper, Jul 22 '13 at 10:48
@WebDeveloper http://gs.statcounter.com/#browser-ww-monthly-201206-201306 - only 25%, worldwide. — Shadow The GPT Wizard, Jul 22 '13 at 10:52
@ShadowWizard - "Only" 25%? That makes it the second-most popular browser. Even if it was "only" 10% you couldn't really disregard it from a website development point of view. — nnnnnn, Jul 22 '13 at 11:23
@nnnn I don't disregard it, I just dislike it and happy it's becoming less and less popular. — Shadow The GPT Wizard, Jul 22 '13 at 11:36

score 2 · Accepted Answer · answered Jul 22 '13 at 10:35

"but how do i fix a "object doesn't support this property or method" in general"

Given an object obj, you can test whether property/method prop exists with:

if ("prop" in obj) {
    // do something with obj.prop
}

...noting that the in operator will check inherited properties too. To check only for direct properties use:

if (obj.hasOwnProperty("prop")) {
    // do something with obj.prop
}

"is there a way to check if the variable external exists"

In the case of the external property you mentioned, it will be a property of window if it exists, so:

if ("external" in window) {
   // do something
}

This x in window technique works for global variables including ones provided by the browser and user-defined ones. It doesn't work on local variables.

Yes. In general terms, a JS object's "methods" are really just properties that happen to refer to functions. — nnnnnn, Jul 22 '13 at 11:20

what is variable "external" meant for in javascript

1 Answers1