计算对象数组中的不同属性

Question

我有以下对象数组

const users = [
 { name: 'Bob Johnson', occupation: 'Developer' },
 { name: 'Joe Davidson', occupation: 'QA Tester' },
 { name: 'Kat Matthews', occupation: 'Developer' },
 { name: 'Ash Lawrence', occupation: 'Developer' },
 { name: 'Jim Powers', occupation: 'Project Manager}]

我想创建一个对象来存储不同类型的唯一计数occupations,就像这样

{ developerCount: 3, qaTesterCount: 1, projectManagerCount: 1 }

我目前的解决方案是这个漫长而长大的方法

let occupationCounts = {
  developerCount: 0,
  qaTesterCount: 0,
  projectManagerCount: 0
}

// Loop through the array and count the properties
users.forEach((user) => {
  switch(user.occupation){
    case 'Developer':
      occupationCounts.developerCount++;
      break;
      // and so on for each occupation
  }
}); 

这种方法只会增加occupation我必须添加的每种新类型.

有一个更简单的解决方案吗？(纯javascript或Lodash Wizardry)

任何输入都表示赞赏!

Answer 1

Array.prototype.reduce 应该在这里提供帮助,只要你不拘泥于具体的计数名称:

const users = [
 { name: 'Bob Johnson', occupation: 'Developer' },
 { name: 'Joe Davidson', occupation: 'QA Tester' },
 { name: 'Kat Matthews', occupation: 'Developer' },
 { name: 'Ash Lawrence', occupation: 'Developer' },
 { name: 'Jim Powers', occupation: 'Project Manager'}
]

const counts = users.reduce((counts, {occupation}) => {
  counts[occupation] = (counts[occupation] || 0) + 1;
  return counts
}, {})

console.log(counts)

虽然你可以做些什么来改变这些名字,但除非真的很重要,否则我不会打扰.

编辑

如果你真的想要那些,你可以得到这样的东西:

const key = occupation[0].toLowerCase() +
            occupation.slice(1).replace(/\s/g, '') + 'Count'
counts[key] = (counts[key] || 0) + 1;

但即使这样也会生成"q A TesterCount"而不是"q a TesterCount".一般来说,走得更远是一个真正的挑战.