int.js

function calculo()

var n1 = parseInt(document.getElementById('n1').value);
var n2 = parseFloat(document.getElementById('n2').value);
var base1  = parseInt(document.getElementById('const1').value);
var base2  = parseFloat(document.getElementById('const2').value);

n1 -= base1;
n2 -= base2;

alert(n1);
alert(n2);