New ecmascript recommendation:

New ecmascript recommendation:

[42, …undefined] –> [42]

This is to make it consistent with:

{ a: 42, …undefined } –> { a: 42 }

As opposed to throwing a TypeError exception. I’m not sure this new behaviour is a great move but I think it’s because:

Object.assign({ a: 42 }, undefined) –> { a: 42 }

https://github.com/tc39/ecma262/pull/1069

https://github.com/tc39/ecma262/pull/1069