javascript - 为什么在 “LocalStorage” 中添加/删除元素不起作用？

Question

我要添加:localStorage中用户的姓名、电话和邮箱使用方法:addContact()以及 localStorage 中的数据，我使用方法 show() 创建表.

也不会发生删除联系人的情况，我正在尝试使用以下方法:deleteContact(e) 。

• 当我添加联系人时，我收到以下错误:Uncaught TypeError: Cannot read property 'value' of undefined
• 删除时收到以下错误:Uncaught TypeError: Cannot read property 'splice' of undefined

帮我解决这个问题

//Product Creation Class
class LocalStorage {
    constructor(name, phone, email) {
        this.name = name;
        this.phone = phone;
        this.email = email;

    }
}
// Сlass where products are recorded
class Book {
    constructor() {

        this.products = [];
        this.name = document.getElementById("name");
        this.phone = document.getElementById("phone");
        this.email = document.getElementById("email");
        this.buttAdd = document.getElementById("add");
        this.book = document.getElementById("addBook");
    }

    //method for adding a product
    addContact() {
        let isNull = this.name.value != '' && this.phone.value != '' && this.email.value != '';
        if (isNull) {
            let obj = new LocalStorage(this.name.value, this.phone.value, this.email.value);
            this.products.push(obj);
            localStorage['addbook'] = JSON.stringify(this.products);
            this.show();
        }
    }

    //method for remove product by name
    deleteContact(e) {
        if (e.target.className === "delbutton") {
            let remID = e.target.getAttribute('data-id');
            this.products.splice(remID, 1);
            localStorage['addbook'] = JSON.stringify(this.products);
            this.show();
        }
    }

    // method to draw the table with product property (
    // name, phone, email)
    show() {
        if (localStorage['addbook'] === undefined) {
            localStorage['addbook'] = '';
        } else {
            this.products = JSON.parse(localStorage['addbook']);

            this.book.innerHTML = '';
            for (let e in this.products) {
                let table = `          <table id="shop" class="entry">
                <tr>
                    <th>Name:</th>
                    <th id="filter">Phone:</th>
                    <th>Email:</th>
                    <th class="dels"></th>
                </tr>
                <tbody>
                <tr class="data">
                <td>${this.products[e].name}</td>
                <td>${this.products[e].phone}</td>
                <td>${this.products[e].email}</td>
                <td class="del"><a href="#" class="delbutton" data-id="' + e + '">Delete</a></td>
</tr>
</tbody>
            </table>`;
                this.book.innerHTML += table;
            }
        }

    }

    OperationsWithContacts() {
        // add new product by click
        this.buttAdd.addEventListener('click', this.addContact);
        // delete product by name after click
        this.book.addEventListener('click', this.deleteContact);
        console.log(this.products);
    }
}

let shop = new Book();
shop.show();
shop.OperationsWithContacts();

<div class="Shop">
    <div class="add-product">
        <h1>Add product</h1>
        <form name="addForm">
            <label for="name" >Name of product</label>
            <input type="text"  id="name" class="input-product">
            <label for="phone">Price of product</label>
            <input type="number" id="phone" class="input-product">
            <label for="email">Count of product</label>
            <input type="text" id="email" class="input-product">
            <button id="add" type="button">Add</button>
        </form>
    </div>
    <div class="product-table">
        <h2>Address book</h2>
        <div id="delete-form">
            <label for="name-delete">Search product by name</label>
            <input type="text" id="name-delete" class="input-delete">
        </div>
        <div id="addBook"></div>
    </div>
</div>

enter code here

Answer 1

我看到的明显问题是，您的函数 addContact() 和 deleteContact() 中的 this 代表一个 button-HTML-Element 而不是您认为的类。

只需稍微更改一下代码，您就会看到://添加产品的方法

addContact() {
    console.log('addContact()', this);

    let isNull = this.name.value != '' && this.phone.value != '' && this.email.value != '';
    if (isNull) {
        let obj = new LocalStorage(this.name.value, this.phone.value, this.email.value);
        this.products.push(obj);
        localStorage['addbook'] = JSON.stringify(this.products);
        this.show();
    }
}

所以你可能想改变你的绑定(bind):

document.querySelector('#add').addEventListener('click', this.addContact);

至

document.querySelector('#add').addEventListener('click', this.addContact.bind(this));

正确重用this快捷方式。

编辑:

//Product Creation Class
//REM: Not the best name choice here.. localStorage <> LocalStorage
class LocalStorage{
  constructor(name, phone, email){
    this.name = name;
    this.phone = phone;
    this.email = email
  }
};

//Сlass where products are recorded
class Book{
  constructor(){
    this.products = [];
    this.name = document.getElementById("name");
    this.phone = document.getElementById("phone");
    this.email = document.getElementById("email");
    this.buttAdd = document.getElementById("add");
    this.book = document.getElementById("addBook")
  };

  //method for adding a product
  addContact(){
    let isNull = this.name.value != '' && this.phone.value != '' && this.email.value != '';
    if(isNull){
      let obj = new LocalStorage(this.name.value, this.phone.value, this.email.value);
      this.products.push(obj);
      localStorage['addbook'] = JSON.stringify(this.products);
      this.show();
    }
  };

  //method for remove product by name
  deleteContact(e) {
    if(e.target.className === "delbutton"){
      let remID = e.target.getAttribute('data-id');
      this.products.splice(remID, 1);
      localStorage['addbook'] = JSON.stringify(this.products);
      this.show();
    }
  };

  //method to draw the table with product property (
  //name, phone, email)
  show(){
    if(localStorage['addbook'] === undefined) {
      //REM: An empty string is no valid JSON to be serialised
      localStorage['addbook'] = '[]'
    }
    else{
      this.products = JSON.parse(localStorage['addbook']);
      this.book.innerHTML = '';

      for(let e in this.products){
        let table = `          <table id="shop" class="entry">
          <tr>
          <th>Name:</th>
          <th id="filter">Phone:</th>
          <th>Email:</th>
          <th class="dels"></th>
          </tr>
          <tbody>
          <tr class="data">
          <td>${this.products[e].name}</td>
          <td>${this.products[e].phone}</td>
          <td>${this.products[e].email}</td>
          <td class="del"><a href="#" class="delbutton" data-id="' + e + '">Delete</a></td>
          </tr>
          </tbody>
          </table>`;

        this.book.innerHTML += table;
      }
    }
  };

  OperationsWithContacts(){
    // add new product by click
    this.buttAdd.addEventListener('click', this.addContact.bind(this));

    // delete product by name after click
    this.book.addEventListener('click', this.deleteContact.bind(this));
    console.log(this.products);
  }
};

;window.onload = function(){
  let shop = new Book();
  shop.show();
  shop.OperationsWithContacts()
};

<div class="Shop">
  <div class="add-product">
    <h1>Add product</h1>
    <form name="addForm">
      <label for="name" >Name of product</label>
      <input type="text"  id="name" class="input-product">
      <label for="phone">Price of product</label>
      <input type="number" id="phone" class="input-product">
      <label for="email">Count of product</label>
      <input type="text" id="email" class="input-product">
      <button id="add" type="button">Add</button>
    </form>
  </div>
  <div class="product-table">
    <h2>Address book</h2>
    <div id="delete-form">
      <label for="name-delete">Search product by name</label>
      <input type="text" id="name-delete" class="input-delete">
    </div>
    <div id="addBook"></div>
  </div>
</div>