JavaScript如何合并数组中同属性值对象的属性并去重

原有代码错误点 #

• 变量引用错误：reduce回调的当前项参数是v，你代码里写的i.student中的i未定义，直接会触发语法报错
• 分组key逻辑错误：用student+subject作为分组key，无法实现按「学生+班级」分组的预期效果，也没法把多科目分数聚合到同一个对象中
• 未保留同学生全科目分数：原有逻辑只会保留当前条目的科目分数，无法把同一个学生其他科目的分数合并到所有对应班级条目里

实现思路 #

1. 先对原始数组做基础去重，过滤掉完全重复的条目
2. 统计每个学生的所有科目分数，生成学生-科目分数的映射表
3. 按「学生+班级」分组生成最终条目，每个条目注入该学生的所有科目分数，同时移除冗余的subject、marks属性

完整实现代码 #

var input = [
  { student: 'Alex', class: 'ten', subject: 'maths', marks: '85', answer: 'Moderate', percentage: '90', sports: 'good' },
  { student: 'Alex', class: 'ten', subject: 'maths', marks: '85', answer: 'Moderate', percentage: '90', sports: 'good' },
  { student: 'Alex', class: 'nine', subject: 'science', marks: '82', answer: 'Severe', percentage: '85', sports: 'good' },
  { student: 'Alex', class: 'nine', subject: 'science', marks: '82', answer: 'Severe', percentage: '85', sports: 'good' },
  { student: 'Alex', class: 'eight', subject: 'computer', marks: '90', answer: 'Extreme', percentage: '87', sports: 'good' },
  { student: 'Alex', class: 'eight', subject: 'computer', marks: '90', answer: 'Extreme', percentage: '87', sports: 'good' },
  { student: 'john', class: 'ten', subject: 'maths', marks: '90', answer: 'Extreme', percentage: '99', sports: 'good' },
  { student: 'john', class: 'ten', subject: 'maths', marks: '90', answer: 'Extreme', percentage: '99', sports: 'good' },
  { student: 'john', class: 'nine', subject: 'science', marks: '85', answer: 'Moderate', percentage: '100', sports: 'good' },
  { student: 'john', class: 'nine', subject: 'science', marks: '85', answer: 'Moderate', percentage: '100', sports: 'good' },
  { student: 'john', class: 'eight', subject: 'computer', marks: '87', answer: 'Extreme', percentage: '67', sports: 'good' },
  { student: 'john', class: 'eight', subject: 'computer', marks: '87', answer: 'Extreme', percentage: '67', sports: 'good' },
]

// 1. 基础去重，过滤完全重复的条目
const uniqueInput = [...new Map(input.map(item => 
  [JSON.stringify(item), item]
)).values()]

// 2. 统计每个学生的所有科目分数
const studentSubjectMap = uniqueInput.reduce((map, item) => {
  if (!map[item.student]) map[item.student] = {}
  map[item.student][item.subject] = item.marks
  return map
}, {})

// 3. 按学生+班级分组生成最终结果
const result = Object.values(uniqueInput.reduce((acc, item) => {
  const groupKey = `${item.student}_${item.class}`
  if (!acc[groupKey]) {
    // 移除冗余的subject、marks字段，注入该学生全科目分数
    const { subject, marks, ...rest } = item
    acc[groupKey] = {
      ...rest,
      ...studentSubjectMap[item.student]
    }
  }
  return acc
}, {}))

console.log(result)

如果需要统一同学生的answer字段取值，可在第二步生成映射表时额外存储对应字段，第三步替换即可

内容的提问来源于stack exchange，提问作者Vishnu Vedagna