ansaurus

Question

How can I verify if a function was defined in JavaScript?

Answer 1

+2 A:

Yes. Functions are just properties of objects like any other, so you can treat them as such. The conditional you posted above will return true if that function (or any member of window.opener called MyFunctionBlah) is defined and non-null.

Marc W 2009-05-25 19:19:32

Technically, non-null, non-false, non-zero, and non-empty-string... but hopefully, any name that looks like a function would actually be a function if it exists.

Matthew Crumley 2009-05-27 14:47:47

Answer 2

+6 A:

if (typeof yourFunctionName == 'function') {
    yourFunctionName();
}

marduk 2009-05-25 19:20:08

If i remember correctly, (typeof function(){}) is 'object' in IE.

I.devries 2009-05-25 20:08:13

Nope, it's "function" as well. I think you're thinking of typeof for arrays.

ajm 2009-05-27 14:22:55

Sorin Mocanu 2009-05-27 15:18:02

Answer 3

+2 A:

if( window.opener.MyFunctionBlah && ... is not necessary because typeof will return 'undefined' if the given property is not defined.

A simple if( typeof window.opener.myFunctionBlah == 'function' is enough.

romac 2009-05-25 19:47:30

ansaurus

tags:

views:

answers:

How can I verify if a function was defined in JavaScript?

related questions