计算JavaScript / NodeJS / Underscore中的散列值
我有一个ruby数组，看起来像这样：
domains = [ { "country" => "Germany"}, {"country" => "United Kingdom"}, {"country" => "Hungary"}, {"country" => "United States"}, {"country" => "France"}, {"country" => "Germany"}, {"country" => "Slovakia"}, {"country" => "Hungary"}, {"country" => "United States"}, {"country" => "Norway"}, {"country" => "Germany"}, {"country" => "United Kingdom"}, {"country" => "Hungary"}, {"country" => "United States"}, {"country" => "Norway"} ] 编辑：：
所以如果以这种格式（从CouchDB）返回：
domains= {"total_rows":55717,"offset":0,"rows": [ {"country":"Germany"}, {"country":"United Kingdom"}, {"country":"Hungary"}, {"country":"United States"},\ \ {"country":"France"}, {"country":"Germany"}, {"country":"Slovakia"}, {"country":"Hungary"}, {"country":"United States"}, {"country":"Norway"}, {"country":"Germany"}, {"country":"United Kingdom"}, {"country":"Hungary"}, {"country":"United States"}, {"country":"Norway"}] }
我怎样才能应用相同的过程。 即获取到embedded数组中的项目？
使用Ruby我可以在数组上进行交互，并删除重复的值，如下所示：
counted = Hash.new(0) domains.each { |h| counted[h["country"]] += 1 } counted = Hash[counted.map {|k,v| [k,v.to_s] }]
其输出如下所示：
{"Germany"=>"3", "United Kingdom"=>"2", "Hungary"=>"3", "United States"=>"3", "France"=>"1", "Slovakia"=>"1", "Norway"=>"2"}
我的问题是什么是最好的方式来实现相同的使用JavaScript可能使用像下划线库？
最好的祝福，
Carlskii
只是循环的值，并增加一个哈希计数。
var count = {}; domains.forEach(function (obj) { var c = obj.country; count[c] = count[c] ? count[c] + 1 : 1; });
（请注意，IE 8及更早版本不支持forEach ，如果您关心它们，请使用polyfill或常规for循环）
你也可以像使用Ruby一样使用reduce函数：
domains.reduce(function(country_with_count, country_object) { country_with_count[country_object['country']] = (country_with_count[country_object['country']] || 0) + 1; return country_with_count; }, {});