How to check whether a JavaScript function exists in Parent Window

Question

I am currently working on a web forms application. I have Javascript function [e.g HideWaitMessage() ] in the parent window. I use window.parent.HideWaitMessage() from child window to access this and it works as expected.

However, in order to avoid errors, I wanted to verify whether the function does exist in the parent window. Please advise on how I can achieve this.

score 2 · Answer 1 · edited Nov 01 '17 at 02:41

2

Have you tried checking

if (typeof window.parent.HideWaitMessage === 'function') {
// sage to use
}

edited Nov 01 '17 at 02:41

Chava Geldzahler

3,605
1
18
32

answered Nov 01 '17 at 02:40

gie3d

766
4
8

Thanks that did the trick. – sam Nov 01 '17 at 02:46

dhilt · Answer 2 · 2017-11-01T02:43:18.770

1

I would use the following protection

window.parent && typeof window.parent.HideWaitMessage === 'function'

edited Nov 01 '17 at 02:43

answered Nov 01 '17 at 02:37

dhilt

18,707
8
70
85

In what circumstances would `window` be falsy? – nnnnnn Nov 01 '17 at 02:40
@nnnnnn Nodejs or some specific environment? – dhilt Nov 01 '17 at 02:41
In Node.js wouldn't `window` not be defined at all and thus result in a reference error? Anyway, I think it's fairly clear the OP is describing a browser-based scenario. – nnnnnn Nov 01 '17 at 02:42
@nnnnnn You are right, thanks... – dhilt Nov 01 '17 at 02:44
Yes that solved it Thanks – sam Nov 01 '17 at 02:45

How to check whether a JavaScript function exists in Parent Window

2 Answers2