floor
This function returns the largest integral value that is not greater than x.
double floor(double x)
Parameters:
x
The number to round.
Return value:
The largest integral value not greater than x.
Remarks:
This function will always decrease x, except where x is already an integer. For example, the floor of 5.9 will be 5, but the floor of -5.9 will be -6.
Example:

    void main()
    {
    alert("floor test", "floor of 5.9 is "+floor(5.9)+".");
    alert("floor test", "floor of 5 is "+floor(5)+".");
    alert("floor test", "floor of -5.9 is "+floor(-5.9)+".");
    }