+1

you can use Math.min(
array) this way instead of apply

you're 4 kyu so a 30 minute problem can either be 5kyu or 6 kyu easily so it's not outrageous. And if it's not outrageous no need to cherry pick

RegExp don't work like that brother. It will just check only one single character inside the bracket as if you write like you've shown. Check https://regexlearn.com/cheatsheet .

Awesome

to ignore the uppercase with the lower case, because A !=a in JS

Different possible reasons. Maybe you're more familiar with some concepts than others (every person is different). Also, keep in mind that you can check the date when the kata was published on the Details page, on the left of each kata. Newer katas (from last years) are more difficult than katas published more than 8 years ago. This one, for example, was published in 2013. There is kind of a new standard right now, so this kata would probably not be ranked more than 7 kyu if it would be published today. But re-ranking a kata is not possible.