演算子を関数にする関数 ref: http://qiita.com/alucky0707/items/2e38690acdd9f0eb2725

op2fn.js

function curry (fn) {
  return function curried() {
    var
    args = Array.prototype.slice.call(arguments, 0);
    return args.length >= fn.length ? fn.apply(this, arguments)
      : function () {
        return curried.apply(this, args.concat(Array.prototype.slice.apply(arguments)));
      };
  };
}
function op(o) {
  return curry(Function('x, y', 'return x ' + o + 'y;'));
}

op2js-usage.js

var
xs = [1,2,3,4,5];

console.log(xs.reduce(op('*'))); //=> 120
console.log(xs.map(op('+')(10))); //=> [11,12,13,14,15]