What could be the reason behind the malfunctioning of a custom filter in this specific Vue 3 application?

In my development project, I am creating a Vue 3 CRUD application for managing Users. The goal is to display the users in reverse order so that the newest additions appear at the top. To achieve this, I have implemented a custom filter as shown below:

reverse(array) {
  return array.slice().reverse();
}

However, instead of getting the desired result, I encountered an error stating

Property "reverse" was accessed during render but is not defined on instance
.

I've set up the data structure for the users and included methods for form validation and adding new users as well. Here's a snippet of the code:
.logo {
  width: 30px;
}

.nav-item {
  width: 100%;
}

@media (min-width: 768px) {
  .nav-item {
    width: auto;
  }
}

.user-row {
  transition: all 1s ease;
  opacity: 1;
  height: auto;
}

.user-row-active {
  opacity: 0;
  height: 0;
}

.alert {
  padding: 0.6rem 0.75rem;
  text-align: center;
  font-weight: 600;
}
The code further includes HTML markup for displaying user details in a table format and a modal window for adding new users.

Questions:

  1. What could be the issue causing the error message?
  2. Are there any alternative approaches to achieving the desired reverse order display without using a filter?

Answer №1

According to the documentation, filters in Vue.js are primarily used for text formatting and cannot be applied directly to array elements. Instead, computed properties offer an alternative solution to achieve a reversed array.

To implement this, you can create a computed property like so:

reversedUsers() {
  return this.users.slice().reverse();
}

You can then access the results as shown below:

// Your complete code snippet goes here
.logo {
  width: 30px;
}

.nav-item {
  width: 100%;
}

@media (min-width: 768px) {
  .nav-item {
    width: auto;
  }
}

.user-row {
  transition: all 1s ease;
  opacity: 1;
  height: auto;
}

.user-row-active {
  opacity: 0;
  height: 0; 
}

.alert {
  padding: 0.6rem 0.75rem;
  text-align: center;
  font-weight: 600;
}
<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.4.1/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
<script src="https://unpkg.com/vue@next"></script>


<div id="app">
  <nav class="navbar navbar-expand-sm bg-dark navbar-dark">
    <!-- Brand -->
    <a class="navbar-brand p-0" href="#">
      <img src="https://www.pngrepo.com/png/303293/180/bootstrap-4-logo.png" alt="" class="logo">
    </a>

    <!-- Links -->
    <div class="navbar-nav w-100">
      <ul class="navbar-nav ml-auto" id="navbarSupportedContent">
        <li class="nav-item">
          <button type="button" class="btn btn-sm btn-success" data-toggle="modal" data-target="#exampleModalCenter">
            Add user
          </button>
        </li>
      </ul>
    </div>
  </nav>

  <div class="container">
    <div class="card my-2">
      <h5 class="card-header px-2">Users</h5>
      <div class="card-body p-0">
        <table class="table table-striped m-0">
          <thead>
            <tr>
              <th>Firstname</th>
              <th>Lastname</th>
              <th>Email</th>
            </tr>
          </thead>
          <tbody name="users-table" is="transition-group">
            <tr v-for="user in reversedUsers" :key="user.id" class="user-row">
              <td>{{user.first_name}}</td>
              <td>{{user.last_name}}</td>
              <td>{{user.email}}</td>
            </tr>
          </tbody>
        </table>
      </div>
    </div>
  </div>

  <div class="modal fade" id="exampleModalCenter" tabindex="-1" role="dialog" aria-labelledby="exampleModalCenterTitle" aria-hidden="true">
    <div class="modal-dialog modal-dialog-centered" role="document">
      <div class="modal-content">
        <div class="modal-header">
          <h3 class="modal-title h6" id="exampleModalLongTitle">New User</h3>
          <button type="button" class="close" data-dismiss="modal" aria-label="Close" @click="resetAddFormData">
            <span aria-hidden="true">&times;</span>
          </button>
        </div>
        <div class="modal-body">
          <div v-if="this.formErrors.length">
            <div v-for="error in formErrors" class="alert alert-danger">
              {{error}}
            </div>
          </div>
          <div v-if="userAdded" class="alert alert-success">User added successfully!</div>
          <form @submit.prevent="addUser" novalidate>
            <div class="form-group mb-2">
              <input type="text" class="form-control input-sm" placeholder="First name" v-model="formData.first_name">
            </div>
            <div class="form-group mb-2">
              <input type="text" class="form-control input-sm" placeholder="Last name" v-model="formData.last_name">
            </div>
            <div class="form-group mb-2">
              <input type="email" class="form-control input-sm" placeholder="Email address" v-model="formData.email">
            </div>
            <div class=" mt-2">
              <button type="submit" class="btn btn-sm btn-block btn-success">Submit</button>
            </div>
          </form>
        </div>
      </div>
    </div>
  </div>

</div>

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