1542817 - `ReferenceError: ga is not defined` on some pages

Status: RESOLVED FIXED

(developer.mozilla.org Graveyard :: General, defect)

Description

[Peter Bengtsson [:peterbe]]

Attachment: Screen Shot 2019-04-08 at 12.27.33 PM.png

Steps to reproduce

1. Open dev tools Web Console
2. Load https://developer.mozilla.org/en-US/docs/Web/HTML/Element/figure with Firefox Content Blocking

ReferenceError: ga is not defined

The screenshot mentioned line is referencing line 91 which isn't right but very near is the line ga('send', 'pageview', {'hitCallback': removeUtms}); which I suspect gets called after window.onload even though ga might not have been created successfully (in the lines above).

Comment 1

[Peter Bengtsson [:peterbe]]

I noticed, it happens on https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach but not https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray

Clicking around, it seems quite random. Repeatable when you refresh the page but varying depending on the page.

Comment 2

[Peter Bengtsson [:peterbe]]

I figured it out. The perf-post-message-handler.js assumes it can use ga without saying where it's coming from. You and I know it comes from window but if you don't say that you get that kind of error.

Comment 3

[GitHub Bugzilla PR Linker]

Attachment: Link to GitHub pull-request: https://github.com/mozilla/kuma/pull/5550

Comment 4

[Peter Bengtsson [:peterbe]]

Landed in master https://github.com/mozilla/kuma/commit/986cdddfd7318f8999ba48a80e4d02e783db54d2

And deployed to prod.

Comment 5

[Peter Bengtsson [:peterbe]]

Turns out, there's a file called perf-post-message-handler.min.js that gets used in production.
https://github.com/mozilla/kuma/blob/master/kuma/static/js/utils/perf-post-message-handler.min.js

Why is this even checked into git?!

Either way, this file is what gets used in production instead of https://github.com/mozilla/kuma/blob/master/kuma/static/js/utils/perf-post-message-handler.js

Comment 6

[Peter Bengtsson [:peterbe]]

We fixed that too.