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法律研究JavaScript 中物件陣列屬性值的新物件陣列之和
假設我們有一個物件陣列，其中包含有關一些學生及其成績的資料，如下所示 −
const arr = [
{ subject: 'Maths', marks: '40', noOfStudents: '5' },
{ subject: 'Science', marks: '50', noOfStudents: '16' },
{ subject: 'History', marks: '35', noOfStudents: '23' },
{ subject: 'Science', marks: '65', noOfStudents: '2' },
{ subject: 'Maths', marks: '30', noOfStudents: '12' },
{ subject: 'History', marks: '55', noOfStudents: '20' },
];我們需要編寫一個 JavaScript 函式，該函式接受這樣一個數組。
該函式應根據物件的“科目”屬性消除冗餘條目。此外，該函式應為該單個物件中的唯一物件新增所有成績和學生數。
因此，對於上述陣列，輸出應該如下所示 −
const output = [
{ subject: 'Maths', marks: '70', noOfStudents: '17' },
{ subject: 'Science', marks: '115', noOfStudents: '18' },
{ subject: 'History', marks: '95', noOfStudents: '43' },
];示例
程式碼如下 −
const arr = [
{ subject: 'Maths', marks: '40', noOfStudents: '5' },
{ subject: 'Science', marks: '50', noOfStudents: '16' },
{ subject: 'History', marks: '35', noOfStudents: '23' },
{ subject: 'Science', marks: '65', noOfStudents: '2' },
{ subject: 'Maths', marks: '30', noOfStudents: '12' },
{ subject: 'History', marks: '55', noOfStudents: '20' },
];
const groupBySubject = (arr = []) => {
const map = {};
let res = [];
res = arr.reduce((acc, val) => {
const { subject, marks, noOfStudents } = val;
const { length: l } = acc;
if(map.hasOwnProperty(subject)){
acc[map[subject]]['marks'] = +marks;
acc[map[subject]]['noOfStudents'] = +noOfStudents;
}
else{
map[subject] = l;
acc.push({
subject: subject,
marks: +marks,
noOfStudents: +noOfStudents
});
};
return acc;
}, []);
return res;
};
console.log(groupBySubject(arr));輸出
控制檯中的輸出如下 −
[
{ subject: 'Maths', marks: 30, noOfStudents: 12 },
{ subject: 'Science', marks: 65, noOfStudents: 2 },
{ subject: 'History', marks: 55, noOfStudents: 20 }
]
更新於： 21-Nov-2020
505 次瀏覽
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