var IsAlmostEqual = function(a, b)

{

  var diff = Math.abs(a - b);

  if (a == b) return true;

  if (diff < 4.94065645841247E-320) return true;

  a = Math.abs(a);

  b = Math.abs(b);

  var smallest = (b < a) ? b : a;

  return diff <= smallest * 1.6777e-12;

}

​

var A = 1;

var B = A + 1.6777e-12 / 2;

​

var C = IsAlmostEqual(A,B);

document.getElementById("A").value = A;

document.getElementById("B").value = B;

document.getElementById("C").value = C;

​