This is the best one I've seen, except for the ommission of newline characters to distinguish and align control flow levels.

Rant: Despite it being a popular belief on codewars, fewer lines does not supercede the importance of consistent alignment to convey meaning and intention. My head shouldn't have to swivel and scan for where the control flow is going next, I should know: all things at this level of the flow start on this column.

If the "puzzle" tag refers to the description, you definitely got it right.

soo true, i just skip all of his katas

This could well be a kata issue but you really need to provide more details.

I have to agree with your comment. His explanation is just with one line but it exress better all description in the task.

Not all smart guy can be a teacher with same reason ^^.

Yes, your code is even faster than mine

Btw I check the performance on jsbench.me, it's a great site

hi, try my mine please, I think I achieved the best speed result

True, I probably didn't know about this method then

You could to use find instead forEach to get selected item

Good observation!

Square Matrix Multiplication

Test case 209917 -> [29917, 0, 1]

"the index i of the digit d you took, i as small as possible"
The digit d is 0. We took 0 at index 1. Why do we return 0?

"the index j (as small as possible) where you insert this digit d to have the smallest number."
We insert it at index 0. Why do we return 1?

Test case 269045 -> [26945, 3, 0] is pretty much the same, but the results make sense. I don't understand why we return [29917, 0, 1] and not [29917, 1, 0]