oh I see, that makes scene. thanks for explaining.

I am checking the current value and previous value.

So you are returning the length of the modified array. And I am guessing because you hvae arr[cIndex-1] that cIndex is always 1 above cValue? if not you will just be comparing the same thing

This is my solution I don't understand where is the problem . get two wrong answer ......

var re = /^(?=.{6,10}$)(?![_.-])[a-z]+[0-9]+$/;

for(var i = 0; i < arr.length; i++){

if(arr[i].match(re) === null) { 
   return false;  
}

}
return true;