javascript - 如何将一个数组转换为另一个数组

Question

我有一个数组:

const arr = [
  { name: "aa", type: "total", count: 28394 },
  { name: "aa", type: "featured", count: 4 },
  { name: "aa", type: "noAnswers", count: 5816 },
  { name: "ba", type: "total", count: 148902 },
  { name: "ba", type: "featured", count: 13 },
  { name: "ba", type: "noAnswers", count: 32527 },
  { name: "cc", type: "total", count: 120531 },
  { name: "cc", type: "featured", count: 6 },
  { name: "cc", type: "noAnswers", count: 24170 }
];


const arrResult = [
  { name: "aa", total: 28394, featured: 4, noAnswers: 5816 },
  { name: "ba", total: 148902, featured: 13, noAnswers: 32527 },
  { name: "cc", total: 120531, featured: 6, noAnswers: 24170 }
];

我想出了这段代码:

let output = [];

const unique = [...new Set(arr.map(item => item.name))];

for(const key of unique) {
  let result = arr.filter(x => {
    return x.name === key;
  });
  output.push({
    name: key,
    // need to get the rest of the properties here
    // total
    // featured
    // noAnswers
  });
}

我唯一想不通的是如何获取属性名称。 有什么想法吗？

Answer 1

你可以尝试这样的事情:

想法:

• 创建一个 hashMap，以便您可以通过 name 对对象进行分组。
• 然后，向该组添加必要的属性。
• 最后，遍历键并创建添加回 name 属性的最终对象。

const arr = [ { name: "aa", type: "total", count: 28394 }, { name: "aa", type: "featured", count: 4 }, { name: "aa", type: "noAnswers", count: 5816 }, { name: "ba", type: "total", count: 148902 }, { name: "ba", type: "featured", count: 13 }, { name: "ba", type: "noAnswers", count: 32527 }, { name: "cc", type: "total", count: 120531 }, { name: "cc", type: "featured", count: 6 }, { name: "cc", type: "noAnswers", count: 24170 } ];

const hashMap = arr.reduce((acc, item) => {
  acc[item.name] = acc[item.name] || {};
  acc[item.name][item.type] = item.count;
  return acc;
}, {});

const result = Object.keys(hashMap).map((name) => Object.assign({}, {name}, hashMap[name] ));

console.log(result)

---

工作:

我正在做的是为每个新的 name 创建一个新对象。所以，这个: acc[item.name] = acc[item.name] || {}; 检查条目是否不可用。

• 如果不可用，返回一个新对象。
• 如果可用，返回相同对象的引用。

因此对于任何给定的名称，您只会指代相同的对象。

现在:acc[item.name][item.type] = item.count 设置属性。由于我们指的是同一个对象，您在一个地方设置属性。所以如果你有重复的条目，比如

[
    { name: "aa", type: "total", count: 28394 },
    { name: "aa", type: "total", count: 123},
]

输出将有 total: 123 而不是。

所以，最后，您的结构如下:

{
  aa: {
    total: <something>,
    feature: <something>,
    ...
  }
}

现在您所要做的就是合并这个对象中的名称并返回值。您还可以创建默认具有 name 属性的对象(由 adiga 完成)。这是我在回答时没有想到的。所以记分而不是回答。