javascript - MYSQL Count As, Group By, JSON 等效

Question

是否有任何等价物

mysql_query("SELECT subcategory, COUNT(*) AS subcate FROM database GROUP BY subcategory");

在 Js-Json 中，我可以计算出有多少个独特的子类别并将它们打印在 JSON 数组中，而无需在 mysql_query 中过滤它们？

假设我从数据库中获取了完整的表格

mysql_query("SELECT * FROM database");

然后我将其放入 json_encode($array); 中，然后我可以计算唯一的子类别并从该 JSON 数组打印它们吗？

JSON 数据

[{"category":"fish","subcategory":"angel","name":"angelfish juvenille"},{"category":"fish","subcategory":"angel","name":"angelfish adult"},{"category":"fish","subcategory":"clownfish","name":"clownfish juvenille"},{"category":"fish","subcategory":"clownfish","name":"clownfish adult"]

Answer 1

您需要对数据列表进行简单的归约。您为每个子类别保留一个带有键的对象，该值是具有该特定子类别的元素的数量:

 var data = [{"category":"fish","subcategory":"angel","name":"angelfish juvenille"},{"category":"fish","subcategory":"angel","name":"angelfish adult"},{"category":"fish","subcategory":"clownfish","name":"clownfish juvenille"},{"category":"fish","subcategory":"clownfish","name":"clownfish adult"}]

var result=  data.reduce((all, element) => { 
   all[element.subcategory] = (all[element.subcategory] || 0) +1;
   return all
}, {});

console.log(result);