floating point equality in js

float_equal.js

var eq = function(n1, n2, decimals) {
  var equal = false;
  if (decimals === undefined) {
    decimals = 15;
  }
  if (decimals) {
    var factor = Math.pow(10, decimals);
    var a = Math.round(n1 * factor) / factor, b = Math.round(n2 * factor) / factor;
    console.log(n1 + ' => ' + a + " :: " + n2 + ' => ' + b);
    equal = a == b;
  } else {
    equal = n1 == n2;
  }
  return equal;
}

Number.equals=eq;
Number.prototype.equals = function(n, d){return eq(this,n,d)};