如何按类别汇总JS对象数组中的支出金额并生成指定格式数组

首先你的原始代码存在两处问题：

• transactions 应当是数组（用[]包裹），否则会触发语法错误
• 第三个交易对象的amount和name字段写反了，正确写法应为"amount": "83", "name": "gas"

修正后的原始数据 #

var transactions = [
  {
    "date": "1-1-2023",
    "amount": "850",
    "name": "rent",
    "category": "housing",
    "notepad": ""
  },
  {
    "date": "1-1-2023",
    "amount": "91",
    "name": "electric",
    "category": "housing",
    "notepad": ""
  },
  {
    "date": "1-1-2023",
    "amount": "83",
    "name": "gas",
    "category": "housing",
    "notepad": ""
  },
  {
    "date": "1-1-2023",
    "amount": "50",
    "name": "car insurance",
    "category": "transportation",
    "notepad": ""
  }
];

实现类别汇总的代码 #

通过遍历交易数据，用对象累加各品类支出，再转换为目标数组格式：

// 初始化存储品类总支出的对象
const categoryTotals = {};

// 遍历交易数据，按品类累加金额
transactions.forEach(transaction => {
  // 将字符串金额转为数字，避免字符串拼接错误
  const amount = parseFloat(transaction.amount);
  const category = transaction.category;
  
  categoryTotals[category] = (categoryTotals[category] || 0) + amount;
});

// 转换为要求的数组格式
var groups = Object.keys(categoryTotals);
var expenses = Object.values(categoryTotals).map(total => total.toString());

// 输出结果
console.log(groups); // ['housing', 'transportation']
console.log(expenses); // ['1024', '50']

注：修正数据后housing类别的实际总和为850+91+83=1024，并非示例中的1000

代码逻辑说明 #

1. 用forEach遍历每笔交易，将字符串类型的金额转为数字后，按品类累加到categoryTotals对象中
2. Object.keys(categoryTotals)提取所有品类名称，生成groups数组
3. Object.values(categoryTotals)提取各品类总金额，转为字符串后生成expenses数组

内容的提问来源于stack exchange，提问作者Michael Schwartz