Javascript运算符优先级技术性

Question

I'm having a hard time understanding what is meant by the combination of Exponentiation and everything else (Multiplication, Division, etc) in group 14 of the Javascript precedence.

Source - MDN

Three questions:

1. What is the meaning of combining the right-to-left and left-to-right associativity in one group?
2. How can the expression 2 ** 3 * 4 be rephrased according to these rules, and still get the same answer? 4 * 2 ** 3 works...is that what's meant?
3. When / how is this not equivalent to the seemingly simpler expedient of giving exponentiation higher precedence?

Answer 1

1) 2 ** 3 ** 4 , being right-to-left associative, is 2 ** (3 ** 4) . 2 / 3 / 4 , being left-to-right associative, is (2 / 3) / 4 .

2/3) I believe 2 ** 3 * 4 is (2 ** 3) * 4 . 2 * 3 ** 4 is 2 * (3 ** 4) (as evaluated by es6fiddle ).

This does not follow from the table; but exponentiation should have precedence over multiplication. Mixing left-to-right and right-to-left in one precedence rank is strange. In fact, as far as I could see in ES7 drafts , it is not at all treated grammatically the same way as * , / and % , but as a unary operation (!).

Also note that no engines other than Babel and Traceur have support for ** at the current time, so it is mostly academic at this point. MDN is a wiki, and exponentiation operator was added by a Mozillian; but AFAIK since Mozilla doesn't currently support ** , it does not actually document the way Mozilla interprets the language.