What causes the failure of a custom filter in this Vue 3 application?-CodePudding

I am working on a Users CRUD application with Vue 3. I want to display the users in reverse order (the latest addition should be on top) and for this purpose, I use the custom filter bolow:

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

Instead of the desired result, I get a Property "reverse" was accessed during render but is not defined on instance error.

const usersApp = {
  data() {
    return {
      users: [{
          id: 1,
          first_name: "John",
          last_name: "Doe",
          email: "[email protected]"
        },
        {
          id: 2,
          first_name: "Jane",
          last_name: "Doe",
          email: "[email protected]"
        }
      ],
      formData: {
        first_name: "",
        last_name: "",
        email: ""
      },
      formErrors: [],
      userAdded: false
    };
  },
  methods: {
    isNotEmpty() {
      return (
        this.formData.first_name &&
        this.formData.last_name &&
        this.formData.email
      );
    },
    isEmail(email) {
      return String(email)
        .toLowerCase()
        .match(
          /^(([^<>()[\]\\.,;:\s@"] (\.[^<>()[\]\\.,;:\s@"] )*)|(". "))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9] \.) [a-zA-Z]{2,}))$/
        );
    },
    formValidation() {
      this.formErrors = [];

      if (!this.isNotEmpty()) {
        this.formErrors.push("There are empty filelds");
      }

      if (this.isNotEmpty() && !this.isEmail(this.formData.email)) {
        this.formErrors.push("The email is invalid");
      }
    },
    resetAddFormData() {
      this.formData.first_name = "";
      this.formData.last_name = "";
      this.formData.email = "";
      this.userAdded = false;
    },
    addUser() {
      // Validate form data
      this.formValidation();

      // Make New User
      let newUser = {
        first_name: this.formData.first_name,
        last_name: this.formData.last_name,
        email: this.formData.email
      };

      // Add new user
      if (!this.formErrors.length) {
        this.users.push(newUser);
        this.userAdded = true;
        window.setTimeout(this.resetAddFormData, 1000);
      }
    }
  },
  watch: {
    users() {
      this.users();
    }
  },
  filters: {
    reverse(array) {
      return array.slice().reverse();
    }
  }
};

Vue.createApp(usersApp).mount("#app");

.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 users | reverse" :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>

Questions:

What am I doing wrong?
Is there a better alternative to using a filter for this purpose?

CodePudding user response：

Well, as the docs say filters can be used for common text formatting, therefore you can't use it over the array element, so the alternative solution to get a reversed array is to use computed properties.

So you can create a computed property like this:

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

Then get the results as below:

Show code snippet

const usersApp = {
  data() {
    return {
      users: [{
          id: 1,
          first_name: "John",
          last_name: "Doe",
          email: "[email protected]"
        },
        {
          id: 2,
          first_name: "Jane",
          last_name: "Doe",
          email: "[email protected]"
        }
      ],
      formData: {
        first_name: "",
        last_name: "",
        email: ""
      },
      formErrors: [],
      userAdded: false
    };
  },
  methods: {
    isNotEmpty() {
      return (
        this.formData.first_name &&
        this.formData.last_name &&
        this.formData.email
      );
    },
    isEmail(email) {
      return String(email)
        .toLowerCase()
        .match(
          /^(([^<>()[\]\\.,;:\s@"] (\.[^<>()[\]\\.,;:\s@"] )*)|(". "))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9] \.) [a-zA-Z]{2,}))$/
        );
    },
    formValidation() {
      this.formErrors = [];

      if (!this.isNotEmpty()) {
        this.formErrors.push("There are empty filelds");
      }

      if (this.isNotEmpty() && !this.isEmail(this.formData.email)) {
        this.formErrors.push("The email is invalid");
      }
    },
    resetAddFormData() {
      this.formData.first_name = "";
      this.formData.last_name = "";
      this.formData.email = "";
      this.userAdded = false;
    },
    addUser() {
      // Validate form data
      this.formValidation();

      // Make New User
      let newUser = {
        first_name: this.formData.first_name,
        last_name: this.formData.last_name,
        email: this.formData.email
      };

      // Add new user
      if (!this.formErrors.length) {
        this.users.push(newUser);
        this.userAdded = true;
        window.setTimeout(this.resetAddFormData, 1000);
      }
    }
  },
  watch: {
    users() {
      this.users();
    }
  },
  computed: {
    reversedUsers() {
      return this.users.slice().reverse();
    }
  }
};

Vue.createApp(usersApp).mount("#app");

.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>

CodePudding user response：

https://v3.vuejs.org/guide/migration/filters.html#_3-x-update Maybe you should use computed