解决TypeError: Cannot read property 'category' of undefined及数组分组问题

原代码报错原因 #

你写的pre.cur.category是错误写法：pre是reduce的累加器对象，cur是当前遍历的数组元素，pre里根本没有cur这个属性，所以访问pre.cur.category必然抛出Cannot read property 'category' of undefined。另外原代码还遗漏了turnover字段的处理，也没按期望转换属性名的大小写。

简洁实现方案 #

用Array.reduce就能高效完成分组和属性转换，代码逻辑清晰：

const a = [
  {id: "2197",name: "AC",currency: "EUR",category: "Equity",illiquidYears: 1.0,turnover: 0.15},
  {id: "2194",name: "Japanese",currency: "EUR",category: "Equity",illiquidYears: 1.0,turnover: 0.15},
  {id: "2221237",name: "Global Credit",currency: "EUR",category: "FixedIncome",illiquidYears: 1.0,turnover: 0.15},
  {id: "7123928",name: "Duration Bonds",currency: "EUR",category: "FixedIncome",illiquidYears: 1.0,turnover: 0.15},
  {id: "1151230",name: "Euro Cash",currency: "EUR",category: "FixedIncome",illiquidYears: 1.0,turnover: 0.15},
  {id: "1151230",name: "Euro Cash",currency: "EUR",category: "Alternatives",illiquidYears: 1.0,turnover: 0.15},
  {id: "`231150",name: "Euro Cash",currency: "EUR",category: "Alternatives",illiquidYears: 1.0,turnover: 0.15},
  {id: "11`21350",name: "Euro Cash",currency: "EUR",category: "Others",illiquidYears: 1.0,turnover: 0.15}
];

const trans = (arr) => {
  return arr.reduce((acc, item) => {
    const category = item.category;
    // 转换为期望的属性格式
    const formattedItem = {
      Name: item.name,
      IlliquidYears: item.illiquidYears,
      Turnover: item.turnover
    };
    // 初始化分类数组（如果不存在）
    acc[category] = acc[category] || [];
    acc[category].push(formattedItem);
    return acc;
  }, {});
};

const b = trans(a);
console.log(b);

代码说明 #

• 核心用reduce遍历数组，acc作为容器存储分组后的结果
• 对每个元素，提取category作为分组键，同时把属性名转换为大写开头的格式
• 用acc[category] = acc[category] || []简化数组初始化逻辑，避免冗余的if判断
• 最后把转换好的元素推入对应分类的数组，返回最终结果

这个实现完全符合你的期望输出，同时解决了原代码的报错问题，代码简洁易维护。

内容的提问来源于stack exchange，提问作者Ae Leung