javascript - regular expression for no more than 2 repeated letters/digits -

i have requirement need handle regex expression no more 2 same letter/digit in xsl file

-no space -does not support special chars. -support (a-z,a-z,0-9),  -require 1 of a-z, -require 1 of 0-9, -no more 2 same letter/digits (i.e bbb fail, bb accepted) 

what have far

(?:[^a-za-z0-9]{1,2}) 

this regex it: ^(?!.*([a-za-z0-9])\1{2})(?=.*[a-z])(?=.*\d)[a-za-z0-9]+$

here's breakdown:

(?!.*([a-za-z0-9])\1{2}) makes sure none of chars repeat more twice in row.

(?=.*[a-z]) requires @ least 1 lowercase letter

(?=.*\d) requires @ least 1 digit

[a-za-z0-9]+ allows letters , digits

edit : removed extraneous .* negative lookahead