JS шаблон мемоизации

memoization.js

function calculation(x, y)
{
    var key = x.toString() + "|" + y.toString();
    var result = 0;
 
    if (!calculation.memento[key])
    {
        for (var i = 0; i < y; ++i) result += x;
        calculation.memento[key] = result;
    }
    return calculation.memento[key];
}
calculation.memento = {};