The behavior of the "checked" attribute in VueJS checkboxes does not always match their actual state

Question

The behavior of the "checked" attribute in VueJS checkboxes does not always match their actual state

In this example, I have created a todo-list with checkboxes that can be checked or unchecked based on whether a task is completed or not.

If you uncheck a checkbox in the "Complete tasks" section, the next checkbox will also appear unchecked even if it is still checked in the "All tasks" section.

To see this issue in action, try unchecking the "Go to the store" task in the "Complete tasks" section. You will notice that the "Clean room" task appears unchecked, although it remains checked in the "All tasks" and holds completed status in the data.

Do you have any suggestions on how to resolve this inconsistency?

javascript vue.js checkbox

Answer 1

Answer №1

One challenge to be aware of is Vue's attempt to optimize and "reuse" the DOM, which may not always work in your favor.

To address this issue, it's essential to include a key for each element within a v-for, allowing Vue to differentiate between individual <li> elements based on their keys.

For more detailed information, refer to the documentation: https://v2.vuejs.org/v2/guide/list.html#Maintaining-State

<html>
<head>
    <title>VueJS</title>
</head>
<body>
<div id="root">
    <h1>All tasks</h1>

    <ul>
        <li v-for="task in tasks" :key="task.id">
            {{ task.description }}
            <input type="checkbox" v-model="task.completed" :id="task.id">
        </li>
    </ul>

    <h1>Complete tasks</h1>

    <ul>
        <li v-for="completeTask in completeTasks" :key="completeTask.id">
            {{ completeTask.description }}
            <input type="checkbox" v-model="completeTask.completed" :id="completeTask.id">
        </li>
    </ul>

    <h1>Incomplete tasks</h1>

    <ul>
        <li v-for="incompleteTask in incompleteTasks" :key="incompleteTask.id">
            {{ incompleteTask.description }}
            <input type="checkbox" v-model="incompleteTask.completed" :id="incompleteTask.id">
        </li>
    </ul>
</div>

<script src="https://unpkg.com/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="84f2f1e1c4b6aab2aab5b6">[email protected]</a>/dist/vue.js"></script>

<script>
  new Vue({
    el: '#root',
    data: {
      tasks: [
        {id: 1, description: 'Go to the store', completed: true},

        {id: 2, description: 'Finish X', completed: false},

        {id: 3, description: 'Do Y', completed: false},

        {id: 4, description: 'Clear inbox', completed: false},

        {id: 5, description: 'Make Z', completed: false},

        {id: 6, description: 'Clean room', completed: true},
      ],
    },

    computed: {
      completeTasks() {
        return this.tasks.filter(task => task.completed);
      },

      incompleteTasks() {
        return this.tasks.filter(task => !task.completed);
      },
    },
  });
</script>
</body>
</html>

Answer 2

One challenge to be aware of is Vue's attempt to optimize and "reuse" the DOM, which may not always work in your favor.

To address this issue, it's essential to include a key for each element within a v-for, allowing Vue to differentiate between individual <li> elements based on their keys.

For more detailed information, refer to the documentation: https://v2.vuejs.org/v2/guide/list.html#Maintaining-State

<html>
<head>
    <title>VueJS</title>
</head>
<body>
<div id="root">
    <h1>All tasks</h1>

    <ul>
        <li v-for="task in tasks" :key="task.id">
            {{ task.description }}
            <input type="checkbox" v-model="task.completed" :id="task.id">
        </li>
    </ul>

    <h1>Complete tasks</h1>

    <ul>
        <li v-for="completeTask in completeTasks" :key="completeTask.id">
            {{ completeTask.description }}
            <input type="checkbox" v-model="completeTask.completed" :id="completeTask.id">
        </li>
    </ul>

    <h1>Incomplete tasks</h1>

    <ul>
        <li v-for="incompleteTask in incompleteTasks" :key="incompleteTask.id">
            {{ incompleteTask.description }}
            <input type="checkbox" v-model="incompleteTask.completed" :id="incompleteTask.id">
        </li>
    </ul>
</div>

<script src="https://unpkg.com/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="84f2f1e1c4b6aab2aab5b6">[email protected]</a>/dist/vue.js"></script>

<script>
  new Vue({
    el: '#root',
    data: {
      tasks: [
        {id: 1, description: 'Go to the store', completed: true},

        {id: 2, description: 'Finish X', completed: false},

        {id: 3, description: 'Do Y', completed: false},

        {id: 4, description: 'Clear inbox', completed: false},

        {id: 5, description: 'Make Z', completed: false},

        {id: 6, description: 'Clean room', completed: true},
      ],
    },

    computed: {
      completeTasks() {
        return this.tasks.filter(task => task.completed);
      },

      incompleteTasks() {
        return this.tasks.filter(task => !task.completed);
      },
    },
  });
</script>
</body>
</html>

The behavior of the "checked" attribute in VueJS checkboxes does not always match their actual state

Answer №1

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