Minified file has broken on IE8

[gkatsev]

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Current behaviour

Steps to reproduce (if the current behaviour is a bug)

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Load up the page in IE8 and notice the error in the console about expecing an identifier

Expected behaviour

No errors

Setup

• OS: Windows 7
• browser: IE8
• socket.io version: 1.7.2

Other information (e.g. stacktraces, related issues, suggestions how to fix)

I found this because karma 1.4.0 started failing on IE8, the investigation and error lead me to socket.io-client, though, now investigating this it seems like it's potentially deeper that the problem occurs.

This must have happened only recently since karma 1.3.0 still works fine. I tried adding screw_ie8: false to the uglify mangle options but it didn't seem to fix it. I'm wondering if some dependency updated to accidentally break IE8 support.

Unfortunately, I can't really investigate any longer right now but I'll try to help out as much as I can.

[darrachequesne]

Yes, that has already been reported here: #1040

I can't seem to find the correct uglifyjs configuration though... (#1042)

[gkatsev]

Oh, I thought I looked but I guess I missed that.

The "correct" config is screw_ie8: false under mangle, however, when i tried it it didn't seem to help. I think there's some dependency or something that is doing something that's breaking things.

[mgol]

@darrachequesne Doesn't --support-ie8 work for UglifyJS?

EDIT: Hmm, that's only a CLI flag, it seems. It's being mapped to screw_ie8: false internally: https://github.com/mishoo/UglifyJS2/blob/1eaa211/bin/uglifyjs#L242-L244

[gkatsev]

I tried it, but I think a dependency of socket.io-client is doing something a bit weird that is now failing in the minified version, even with --support-ie8.
I believe it worked when running it through es3ify but I'm not sure this project wants another dependency and step in the build.

[mgol]

Not sure if it helps but since you already run Babel you could try to use babel-preset-es3.

[gkatsev]

I believe it didn't help either because it only runs on the current package code :(

[darrachequesne]

What's weird it that the unminified version currently passes the tests, but even with screw_ie8: false the minified build does not seem to pass, I get a Error: 'document' is null or not an object in IE7/IE8, which I can't make sense of.

[darrachequesne]

Closed by #1042.

[gkatsev]

Sweet, I'll check it out.