Microsoft® JScript™ % Operator 
Language Reference Version 1

Used to divide two numbers and return only the remainder.
result = number1 % number2The % operator syntax has these parts:
Part Description result Any variable. number1 Any numeric expression. number2 Any numeric expression.
The modulus, or remainder, operator divides number1 by number2 (rounding floatingpoint numbers to integers) and returns only the remainder as result. For example, in the following expression, A (which is result) equals 5.
A = 19 % 6.7For information on when a runtime error is generated by the % operator, see the Operator Behavior table.