Question

我正在尝试从费用数组中提取date，expenseInfo，category和amount。但是我得到expenses.map() is not a function。

下面是代码。

我要去哪里错了？

let expenses = [{
    "user": {
      "id": "5bab847a5b0d2e2ce8b4cbe5",
      "name": "test_user",
      "email": "test@gmail.com",
      "username": "test"
    },
    "date": "07-Sep-2018",
    "expenseInfo": "Starbuck",
    "category": "Restaurants",
    "amount": 15
  },
  {
    "user": {
      "id": "5bab847a5b0d2e2ce8b4cbe5",
      "name": "test_user",
      "email": "test@gmail.com",
      "username": "test"
    },
    "date": "01-Aug-2018",
    "expenseInfo": "Shopping",
    "category": "Michael Kors bag",
    "amount": 90
  }
];

let expensesData = [];
let expenses1 = [];
expensesData.push(expenses);

expenses1 = expensesData.map((expense, index) => {
  `<tr>
          <td>${expense[index].date}</td>
          <td>${expense[index].expenseInfo}</td>
          <td>${expense[index].category}</td>
          <td>${expense[index].amount}</td>
           </tr>`
})

Answer 1

当您将费用记入“费用数据”时，您会在0th index处获得费用。您需要避免使用push或尝试下面的代码

let expenses = [{
        "user": {
          "id": "5bab847a5b0d2e2ce8b4cbe5",
          "name": "test_user",
          "email": "test@gmail.com",
          "username": "test"
        },
        "date": "07-Sep-2018",
        "expenseInfo": "Starbuck",
        "category": "Restaurants",
        "amount": 15
      },
      {
        "user": {
          "id": "5bab847a5b0d2e2ce8b4cbe5",
          "name": "test_user",
          "email": "test@gmail.com",
          "username": "test"
        },
        "date": "01-Aug-2018",
        "expenseInfo": "Shopping",
        "category": "Michael Kors bag",
        "amount": 90
      }
    ];

    let expensesData = [];
    let expenses1 = [];
    expensesData.push(expenses);

    expenses1 = expensesData[0].map((expense, index) => {
      `<tr>
              <td>${expense.date}</td>
              <td>${expense.expenseInfo}</td>
              <td>${expense.category}</td>
              <td>${expense.amount}</td>
               </tr>`
    })

Answer 2

let expenses = [{
    "user": {
        "id": "5bab847a5b0d2e2ce8b4cbe5",
        "name": "test_user",
        "email": "test@gmail.com",
        "username": "test"
    },
    "date": "07-Sep-2018",
    "expenseInfo": "Starbuck",
    "category": "Restaurants",
    "amount": 15
},
{
    "user": {
        "id": "5bab847a5b0d2e2ce8b4cbe5",
        "name": "test_user",
        "email": "test@gmail.com",
        "username": "test"
    },
    "date": "01-Aug-2018",
    "expenseInfo": "Shopping",
    "category": "Michael Kors bag",
    "amount": 90
}
];

let expenses1 = [];
expenses1 = expenses.map((expense) => {
   return `<tr>
          <td>${expense.date}</td>
          <td>${expense.expenseInfo}</td>
          <td>${expense.category}</td>
          <td>${expense.amount}</td>
           </tr>`
})
console.log(expenses1)

Answer 3

我认为您正在尝试这样做。

在Map中，您仅需要返回一些值，然后expense1数组将具有值，否则它将用undefined填充。

let expenses = [{
    "user": {
      "id": "5bab847a5b0d2e2ce8b4cbe5",
      "name": "test_user",
      "email": "test@gmail.com",
      "username": "test"
    },
    "date": "07-Sep-2018",
    "expenseInfo": "Starbuck",
    "category": "Restaurants",
    "amount": 15
  },
  {
    "user": {
      "id": "5bab847a5b0d2e2ce8b4cbe5",
      "name": "test_user",
      "email": "test@gmail.com",
      "username": "test"
    },
    "date": "01-Aug-2018",
    "expenseInfo": "Shopping",
    "category": "Michael Kors bag",
    "amount": 90
  }
];

let expensesData = [];
let expenses1 = [];
expensesData = [...expenses];

expenses1 = expensesData.map((expense, index) => {
  return `<tr>
          <td>${expense.date}</td>
          <td>${expense.expenseInfo}</td>
          <td>${expense.category}</td>
          <td>${expense.amount}</td>
           </tr>`
})

Answer 4

我认为您正在尝试这样做。它对我有用

expenses1 = expensesData[0].map(function(expense, index){return yours statement here});

Answer 5

从您发表的评论中我看到的是，您得到的费用是JSON字符串而不是数组。您必须做JSON.parse(expenses)，然后一切都会按预期进行

expenses = JSON.parse(expenses);

let result = expenses.map((expense, index) => {
  return `<tr>
          <td>${expense[index].date}</td>
          <td>${expense[index].expenseInfo}</td>
          <td>${expense[index].category}</td>
          <td>${expense[index].amount}</td>
           </tr>`
});

console.log(result);

您可以从下面的链接检查普通javascript对象和JSON对象之间的区别

What is the difference between JSON and Object Literal Notation?

What are the differences between JSON and JavaScript object? [duplicate]

.map（）不是函数

5 个答案: