我有对象的简单对象： window.abilities = {
migrate:{
name:"Migrate",
description:"Move your tribe to another area; generate all new resources. Takes one time unit.",
image:"migrate
我有3个简单的类CashRegister，Bill和Position。 CashRegister由Bill对象组成，Bill对象由Position对象组成。他们作为跟随 class CashRegister
def initialize
@bills = []
end
def product_frequency
#???
end
我定义了一个对象，如下所示： var obj = {};
var name = "nonenumerable";
var value = "hello world";
Object.defineProperty(obj, name, {value: value,
writable : true,
enumerable : false,
我有数组数组。假设我想统计出9个中有多少元素等于"a"。 string[][] arr = new string[3][] {
new string[]{"a","b","c"},
new string[]{"d","a","f"},
new string[]{"g","a","a"}
};
我如何使用可枚举扩展方法（Count，Where等），它做什么？