Because ceil is a static method of Math you always use it as Mathceil rather than as a method of a Math object you created Math is not a constructor. The javalangMathrandom method returns a pseudorandom double type number greater than or equal to 00 and less than 10. If the input string begins with 0x or 0X a zero followed by lowercase or uppercase X radix is assumed to be 16 and the rest of the string is parsed as a hexadecimal number.
If the input string begins with 0x or 0X a zero followed by lowercase or uppercase X radix is assumed to be 16 and the rest of the string is parsed as a hexadecimal number.
A let variable will contain undefined if nothing is assigned to it. Typeof b undefined. AddEventlistener expects a function to be given not the execution result of a function unless that is a function itself. When this method is first called it creates a single new pseudorandom-number generator exactly as if by the expression new javautilRandom.