Addition function to avoid inaccuracies of floating point addition.

adder.js

var adder = function(precision) {
  precision |= 0;
  return function() {
    var sum = 0;
    var len = arguments.length;
    while (len--) sum += (arguments[len] * precision) | 0;
    return sum / precision;
  };
};

// Example
0.1 + 0.2; //=> 0.30000000000000004
var add = adder(100);
add(0.1, 0.2); //=> 0.3