IE9 and above should handle it fine, so it's just a matter of time before this problem goes away. In the meantime there are two things you can do: use an editor which highlights this as an error (e.g. Webstorm), or add a pre-commit hook on your code repository which disallows committing code that doesn't pass jslint checks. We use both practices on a 200 kline js codebase, and it has essentially gotten rid of javascript errors at the customer due to bad syntax (as well as those tricky = / == / === issues).