Web addin fails in Outlook for Windows with: "Office.js has not fully loaded"

Question

We created an Outlook web addin and it is working fine in OWA and in Outlook for Mac. On Outlook for Windows however, the addin only shows a blank page.

When attaching a debugger, we get the JavaScript error

Office.js has not fully loaded. Your app must call "Office.onReady() as part of it's loading sequence (or set the "Office.initialize" function").

This is Outlook 2016.

We do call Office.onReady and we also tried inserting an empty body for Office.initialize.

I have a feeling that IE is not happy about the JavaScript we are using (Knockout.js perhaps?). We also tried adding <meta http-equiv="X-UA-Compatible" content="IE=edge"> but all to no avail.

How can I figure out what is going wrong?

Obfuscate

Outlook desktop uses Internet Explorer to show add-ins, and some newer javascript features are not available. Can you test your add-in in OWA using Internet Explorer, and see if you're running into the same issue there? It may be that your add-in is utilizing one of these new features, and that is causing initialization to fail. – Paulino

@OutlookAdd-insTeam-MSFT: That's a good idea. Surprisingly, it actually worked in IE but it did show me a tiny JavaScript error that I fixed and now the addin is working in Outlook as well. Thanks! – Obfuscate

Thanks @Outlook Add-ins Team for this important comment. I was facing the similar issue, so I tried to run the add-in on IE11, and found the issue there, and by resolving that, it worked on Outlook desktop client too. Thanks again. – Revivalism

Answer 1

I was facing the similar issue, so I tried to run the add-in on IE11 (to get the actual reason behind the issue), and found the issue there, and by resolving that, it worked on Outlook desktop client too.

Thanks @Outlook Add-ins Team for the important comment.

Revivalism