[0, 1, 2, 3, 4, 5, 6, 7, 8, 9].match(/[02468]/g) would give the result [0, 2, 4, 6, 8]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9].match(/[02468]/) would give the result [0]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9].match(/[345]+/g) would give the result [345]
Maybe. But as I understand, operations with strings are costly in the means of performance, so FAST means of working with arrays while using the syntax of regular expressions would be nice!