Javascript 如何使用reduce、map或filter创建一个函数来显示和统计数组对象的每个值

发布于06月13日

如何创建一个函数来返回每个品种的编号？

const dogs = [
    {
        name:"Cherry",
        breed:["Shiba", "Poodle"]
    },
    {
        name:"Bolt",
        breed:["Shiba"]
    },
    {
        name:"Pumpkin",
        breed:["Chihuahua", "Poodle"]
    },
    {
        name:"Happy",
        breed:["Poodle"]
    },
    {
        name:"Tofu",
        breed:["German Shepherd"]
    }
];

我想打印每个品种及其数量如下.

{
German Shepherd: 1,
Shiba: 2,
Poodle: 3,
Chihuahua:1
}

编辑:

我开始理解一些概念和功能，但将多个不同的概念结合起来对我来说仍然是一个挑战.

推荐答案

这里不需要reduce、filter或map.

创建一个对象以按品种对分数进行分组.
Iterate over the dogs array，然后迭代每只狗的品种array.如果品种doesn't already exist on the object创建它并将值设置为零.
在"品种"值中添加一个.

对于您关于传入一个单独的breed参数以获取该品种的总数的 comments ，只需稍微修改一下函数即可.

const dogs=[{name:"Cherry",breed:["Shiba","Poodle"]},{name:"Bolt",breed:["Shiba"]},{name:"Pumpkin",breed:["Chihuahua","Poodle"]},{name:"Happy",breed:["Poodle"]},{name:"Tofu",breed:["German Shepherd"]}];

// Pass in the dogs array
// and an optional query string
function getBreedCount(dogs, query) {

  // Grouping object
  const obj = {};

  // Iterate over the dogs, and the breeds
  // updating the grouping object as we go
  for (const dog of dogs) {
    for (breed of dog.breed) {
      obj[breed] ??= 0;
      ++obj[breed];
    }
  }

  // If there is a query argument...
  if (query) {

    // ...and the query string is a key on the object
    // Return a string: `<breed>: <value>`...
    if (obj[query]) return `${query}: ${obj[query]}`;

    // ...otherwise return a message that
    // the breed doesn't exist
    return `${query} doesn't exist`;

  }

  // If there is no query argument
  // return the complete object
  return obj;

}

console.log(getBreedCount(dogs));
console.log(getBreedCount(dogs, 'Poodle'));
console.log(getBreedCount(dogs, 'Shiba'));
console.log(getBreedCount(dogs, 'Bobby Davro'));

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