vue.js data fails to update after clearing

Question

vue.js data fails to update after clearing

Incorporated within my page is a vue.js item that monitors modifications made to a form. The code for this functionality is as follows:

var changes_applied = [];

var changes_applied_block = new Vue({
    name: "ChangesApplied",
    el: '#changes-applied',
    data: {
        items: changes_applied
    },
    methods: {
        remove: function(index) {
            changes_applied.splice(index, 1);
        }
    }
});

Whenever a change is detected, it gets added to the changes_applied array and displays in the "Changes Applied" section as expected. The removal process also functions correctly by invoking the remove method on the vue object.

In addition, there's a separate "clear" button that does not relate to the vue instance. Upon clicking this button, the data source is reset to an empty array using changes_applied = [];

The issue arises after clearing the data with the button. Subsequent modifications or additions to the changes array no longer reflect in the vue component—almost like the vue element is no longer linked to the changes_applied array.

Should there be additional bindings or steps required for proper synchronization, or is there a prescribed "vue way" to reset the vue data without direct manipulation of the source array?

javascript vue.js vuejs2

Answer 1

Answer №1

It's important to note that Vue doesn't react effectively to changes made directly on the changes_applied array. The best practice is to avoid manipulating changes_applied and instead focus on modifying this.items directly. When you reassign the reference of this.items, it can break functionality because Vue no longer recognizes it as the same array.

To properly remove items, utilize a method like this:

methods: {
    remove: function(index) {
        this.items.splice(index, 1);
    }

If you need to reset the array, simply use:

this.items = []

By following these guidelines, your code will behave as expected within the Vue framework.

Answer 2

It's important to note that Vue doesn't react effectively to changes made directly on the changes_applied array. The best practice is to avoid manipulating changes_applied and instead focus on modifying this.items directly. When you reassign the reference of this.items, it can break functionality because Vue no longer recognizes it as the same array.

To properly remove items, utilize a method like this:

methods: {
    remove: function(index) {
        this.items.splice(index, 1);
    }

If you need to reset the array, simply use:

this.items = []

By following these guidelines, your code will behave as expected within the Vue framework.

Answer 3

Answer №2

When you initialize the items array with changes_applied, it is just the default value for items when the instance is created and does not maintain bindings. Therefore, changing the changes_applied will not affect the items array on the vue instance.

For example:

new Vue({
  el: '#app',
  data: function () {
    return {
      items: myArr,
      newItem: ''
    }
  },
  methods: {
    addItem () {
      this.items.push(this.newItem)
      this.newItem = ''
    },
    remove (index) {
      this.items.splice(index, 1)
    },
    clear () {
      this.items = []
    }
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.13/vue.js"></script>
<div id="app">
  <input type="text" v-model="newItem" /> 
  <button @click="addItem">Add</button> 
  <button @click="clear">Clear</button>
  <p v-for="(item, index) in items" @click="remove(index)">{{item}}</p>
</div>
<!-- from outside vue instance-->
<button onClick="clearFromOutside()">clear from outside</button>
<script>
var myArr = ['hola', 'mundo'];
  function clearFromOutside() {
    console.log(myArr)
    myArr = [];
    console.log(myArr)
  }
</script>

Answer 4

When you initialize the items array with changes_applied, it is just the default value for items when the instance is created and does not maintain bindings. Therefore, changing the changes_applied will not affect the items array on the vue instance.

For example:

new Vue({
  el: '#app',
  data: function () {
    return {
      items: myArr,
      newItem: ''
    }
  },
  methods: {
    addItem () {
      this.items.push(this.newItem)
      this.newItem = ''
    },
    remove (index) {
      this.items.splice(index, 1)
    },
    clear () {
      this.items = []
    }
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.13/vue.js"></script>
<div id="app">
  <input type="text" v-model="newItem" /> 
  <button @click="addItem">Add</button> 
  <button @click="clear">Clear</button>
  <p v-for="(item, index) in items" @click="remove(index)">{{item}}</p>
</div>
<!-- from outside vue instance-->
<button onClick="clearFromOutside()">clear from outside</button>
<script>
var myArr = ['hola', 'mundo'];
  function clearFromOutside() {
    console.log(myArr)
    myArr = [];
    console.log(myArr)
  }
</script>

Answer 5

Answer №3

Mark_M has already provided a detailed explanation, so I will showcase a demo to make it easier to grasp the concept.

Instead of directly manipulating the array values, you can copy them to a separate data variable and perform all operations on that data:

const changes_applied = [
  {id: 1},
  {id: 2},
  {id: 3}
];

const vm = new Vue({
  el: '#app',
  data: {items: changes_applied},
  methods: {
    add() {
      const id = this.items.length + 1
      this.items.push({id})
    },
    remove() {
      this.items.pop()
    },
    clear() {
      this.items = []
    }
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.13/vue.js"></script>

<div id="app">
  <div>
    <button type="button" @click="add">Add</button>
    <button type="button" @click="remove">Remove</button>
    <button type="button" @click="clear">Clear</button>
  </div>
  <ul name="list">
    <li v-for="item in items" :key="item.id">
      Item {{ item.id }}
    </li>
  </ul>
</div>

Answer 6

Mark_M has already provided a detailed explanation, so I will showcase a demo to make it easier to grasp the concept.

Instead of directly manipulating the array values, you can copy them to a separate data variable and perform all operations on that data:

const changes_applied = [
  {id: 1},
  {id: 2},
  {id: 3}
];

const vm = new Vue({
  el: '#app',
  data: {items: changes_applied},
  methods: {
    add() {
      const id = this.items.length + 1
      this.items.push({id})
    },
    remove() {
      this.items.pop()
    },
    clear() {
      this.items = []
    }
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.13/vue.js"></script>

<div id="app">
  <div>
    <button type="button" @click="add">Add</button>
    <button type="button" @click="remove">Remove</button>
    <button type="button" @click="clear">Clear</button>
  </div>
  <ul name="list">
    <li v-for="item in items" :key="item.id">
      Item {{ item.id }}
    </li>
  </ul>
</div>

vue.js data fails to update after clearing

Answer №1

Answer №2

Answer №3

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