alpha25+ requires ECMAScript 2018

[john-shaffer]

348a673 introduced the use of Unicode property escapes in a regular expression.

https://github.com/mui-org/material-ui-x/blob/f62c6ba3965d25490380da93ea6968166f3ff4a9/packages/grid/_modules_/grid/utils/keyboardUtils.ts#L16

This change means that projects using DataGrid/XGrid have to be compiled to ES9 or later, whereas in v4.0.0-alpha24 ES5 seems to work fine. Considering the widespread usage of Material UI and the drastic change in compatibility, this could be a problem for a lot of projects.

I couldn't find any information on what versions Material UI intends to be compatible with or if this would be considered a bug, so this issue can help document those things as well.

[oliviertassinari]

It's actually a bug in TypeScript: microsoft/TypeScript#32214.

I couldn't find any information on what versions Material UI intends to be compatible with or if this would be considered a bug, so this issue can help document those things as well.

https://next.material-ui.com/getting-started/supported-platforms/#browser vs. https://caniuse.com/mdn-javascript_builtins_regexp_property_escapes it looks like we are good.

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This also resonates with #50, Babel handles the problem correctly. In the core, we use .browserslistrc with Babel to transpile what we need, a feature TypeScript doesn't support: microsoft/TypeScript#19183 either.

[john-shaffer]

Thank you for the quick response!