Building An Interest Rate Calculator, However It Won't Produce Figure

I am building trying to build a calculator that calculates a monthly payment based on an interest rate when clicking on a button, I'm using basic javascript bootstrap. I have alrea

Solution 1:

Just remove () while calling document.getElementById("pp").value() as

var pp = document.getElementById("pp").value;
  var dp = document.getElementById("dp").value;
  var mt = document.getElementById("mt").value;
  var ir = document.getElementById("ir").value;

value is not a function. Here is a link to a working plunker