Which feature of JavaScript can we use in Custom Widget?

I run my Apps on Windows Tulip Player and iOS Tulip Player.
I want my Custom Widgets to run safely on both Players.
Is there a easy way to know which Tulip Player version supports which JavaScript features?

For instance, can I use “Spread syntax”?
Spread syntax (…) - JavaScript | MDN

I became afraid about this because the editor does not understand it.