reduce sum and product

reduce.js

/**
* Walk through a list, running an associative function on each item, and returning the result
* @param {function} func A function in the form of f(x,y) to be applied to each item and its successor in list
* @param {Object[]} list The array to have the function applied to
* @param The y value of an object passed into <tt>func</tt> when x is the last item in the list
* @returns An object containing the result of <tt>func</tt> applied to <tt>list</tt>
*/
var reduce=function(func,list,nilval) {
  var len=list.length,
  i=0,
  r=nilval;
  for(;i<len;i+=1) {
    r=func(r,list[i]);
  }
  return r;
};


var add=function(x,y) {
    return x+y;
};

var sum=function(list) {
  return reduce(add,list,0);
};

var multiply=function(x,y) {
    return x*y;
};

var product=function(list) {
  return reduce(multiply,list,1);
};