.forEach(), converting string to array, array-like object to array, etc, etc are super bloats and not healthy for Golfing.
ES6+, on the other hand, has some super handy features and reduced footprint.
[...x], etc. are just some of the examples.
Please post some nice tricks that can help shave off those few extra bytes from your code.
However, this thread is also for users who currently golf using ES5 features. Answers may also contain tips to help them understand and map ES6 features to their style of ES5 coding.