查找对象中重复属性值的计数 [英] Find the count of duplicate property values in an object

问题描述

var db = [
  {Id: "201" , Player: "Nugent",Position: "Defenders"},
  {Id: "202", Player: "Ryan",Position: "Forwards"},
  {Id: "203" ,Player: "Sam",Position: "Forwards"},
  {Id: "204", Player: "Bill",Position: "Midfielder"},
  {Id: "205" ,Player: "Dave",Position: "Forwards"},
];

如何按Position查找重复对象的数量.

How can I can I find the number of duplicate objects by Position.

请注意，我有重复的值作为"Forwards"(第二个，第三个和最后一个对象)

Notice I have duplicated value as "Forwards" (second, third and last object)

我尝试做:

for (var key in db) {
  var value = db[key];
  if ( count of duplicated values == 3) {
    console.log("we have three duplicated values)
  }
}

在循环对象时是否可以这样做?

Is it possible to do this while the objects are being looped?

推荐答案

使用另一个对象作为计数器，

Use another object as a counter, like this

var counter = {};
for (var i = 0; i < db.length; i += 1) {
    counter[db[i].Position] = (counter[db[i].Position] || 0) + 1;
}

for (var key in counter) {
    if (counter[key] > 1) {
        console.log("we have ", key, " duplicated ", counter[key], " times");
    }
}

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