"'documentMode' in document" check giving inconsistent results

[SchleyB]

Bug

What is the current behavior?

Line 124 of ChangeEventPlugin.js

isInputEventSupported = isEventSupported('input') && (!('documentMode' in document) || document.documentMode > 11);

Is incorrectly returning false in non-IE browsers when paired with some 3rd party code, specifically

!('documentMode' in document)

Is returning false because Google Tag Manager in this case is setting document.documentMode to undefined. This is causing these errors on input fields

Uncaught TypeError: activeElement.detachEvent is not a function
TypeError·Uncaught TypeError: Cannot delete property 'value' of #<HTMLInputElement>

A better check in this case might be

!document.documentMode

As this would still accomplish the intended check while minimizing conflicts with other codebases

I have found a couple of other instances of this issue:
#7421
#5920

*Which versions of React, and which browser / OS are affected by this issue? *

Chrome 52
React 15.3.1

[gaearon]

Would you like to send a PR?

[SchleyB]

Sure thing...7594

[zpao]

That's merged so we can close this out. Thanks!