フックの法石計算機

I want to calculate
Spring Force Constant(k) = N/m
Distance from Equilibrium(x) = m
Spring Equilibrium Position(x0) = m
Force(Fx) = N
   
function checnum(as)
{
var dd = as.value;

if(isNaN(dd))
{
dd = dd.substring(0,(dd.length-1));
as.value = dd;
}
}

function calsi()
{
var ty = doc