如何在JavaScript中計算物件陣列的屬性

var employees = [
{ name: "Josh", title: "receptionist" },
{ name: "Naila", title: "receptionist" },
{ name: "Tom", title: "doctor" },
{ name: "Becky", title: "doctor" }
];

{
    'doctor':2,
    'receptionist':2
}

這是我嘗試過的：

const convert = (employees) => {
    const res = {};
    employees.forEach((employee) => {
        const key = `${employee.title}${employee["doctor-receptionist"]}`;
            if (!res[key]) {
                res[key] = {...employee, count: 0 };
            };
            res[key].count  = 1;
        });
    return Object.values(res);
};
console.log(convert(employees));

它回傳員工的姓名，這是我不想要的。我還考慮為每種職位創建陣列，并從員工陣列中過濾每個員工，然后將它們推送到各自的陣列中。但我覺得必須有一個更簡單的方法。

uj5u.com熱心網友回復：

只要使用reduce()就可以做到

var employees = [
  { name: "Josh", title: "receptionist" },
  { name: "Naila", title: "receptionist" },
  { name: "Tom", title: "doctor" },
  { name: "Becky", title: "doctor" }
]; 

let result = employees.reduce((a,c) =>{
   a[c.title] = a[c.title] ? a[c.title]   1 : 1
  return a
},{})

console.log(result)

uj5u.com熱心網友回復：

reduce迭代器是為這種事情而構建的 。https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce

我也采用Object.values()了，因為我使用 reduce 的方式是創建一個物件以輕松跟蹤沿途的資料。完成后有助于將其object.values提取到陣列中。

const employees = [
  { name: "Josh", title: "receptionist" },
  { name: "Naila", title: "receptionist" },
  { name: "Tom", title: "doctor" },
  { name: "Becky", title: "doctor" }];
  
const reduced = Object.values(employees.reduce((b,a) => {
if (!b[a.title]) b[a.title] = {title: a.title, count: 1}
else b[a.title].count  ;
return b
},{}))

console.log(reduced);
  

uj5u.com熱心網友回復：

你可以在你的代碼上試試這個

const employees = [
    { name: "Josh", title: "receptionist" },
    { name: "Naila", title: "receptionist" },
    { name: "Tom", title: "doctor" },
    { name: "Becky", title: "doctor" }
]  


const sumReceptionist = employees.filter((item)=>{
    return item.title === 'receptionist'
}).length
const sumDoctor = employees.filter((item)=>{
    return item.title === 'doctor'
}).length

let total =
    {
        receptionist: sumReceptionist,
        doctor: sumDoctor
    }

console.log(total)

uj5u.com熱心網友回復：

我認為這就是你想要做的。您想要員工串列中的職位總數嗎？

const Employees = [{
    name: "Josh",
    title: "receptionist"
  },
  {
    name: "Naila",
    title: "receptionist"
  },
  {
    name: "Tom",
    title: "doctor"
  },
  {
    name: "Becky",
    title: "doctor"
  },
  {
    name: "Chad",
    title: "doctor"
  },
  {
    name: "Cindy",
    title: "nurse"
  }
];

// A forEach won't return an object or array, so we create one to modify within it
const PositionTotals = {};
Employees.forEach(employee => {
  // Check if property exists. If not, create it and add one to it before continuing loop
  if (!PositionTotals.hasOwnProperty(employee.title))
    return PositionTotals[employee.title] = 1;
  PositionTotals[employee.title]  ;
})

console.log(PositionTotals);
$('#PositionTotals').html(JSON.stringify(PositionTotals, null, '\t'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.2.3/jquery.min.js"></script>
<pre id="PositionTotals"></pre>

標籤：javascript数组

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