javaScript question

Read the input from the document. If it is a positive integer, output the factorial of the input value. Otherwise, output Cannot compute factorial value. The factorial function is defined as multiply all the numbers from 1 to the value together. For example, the factorial of 5 is 5*4*3*2*1 = 120. Only compute this value using a loop, no other formulations are allowed.

May I have javascript code and hyml code thanks