Vue.js - Updating parent component from child component using one-way data binding

Question

Vue.js - Updating parent component from child component using one-way data binding

I am curious about the behavior of VueJS2 when using a colon for one-way data binding. In this specific example, I find it interesting that the child component is able to update an array declared in the parent component even though it was passed down as a prop (which should be one-way binding).

https://jsfiddle.net/ecgxykrt/

<script src="https://unpkg.com/vue"></script>

<div id="app">
    <span>Parent value: {{ dataTest }}</span>
    <test :datatest="dataTest" />
</div>

var test = {
    props: ['datatest'],
    mounted: function() {
        this.datatest.push(10)
    },
    render: function() {}
}

new Vue({
    el: '#app',
    components: {
        'test': test
    },
    data: function() {
        return {
            dataTest: []
        }
    }
})

Any insights on this would be greatly appreciated!

javascript vue.js vuejs2

Answer 1

Answer №1

Vue is designed to prevent direct assignment to props, but it does not stop you from accessing a prop's methods or making changes to its elements or properties, all of which can alter the object's contents. However, these actions do not modify the actual value of the prop itself, as it remains a reference to an underlying structure.

An additional issue to note is that Vue is unable to detect modifications to Array elements or additions/deletions of Object members, as explained in this documentation.

For more information, check out this discussion on Stack Overflow.

Answer 2

Vue is designed to prevent direct assignment to props, but it does not stop you from accessing a prop's methods or making changes to its elements or properties, all of which can alter the object's contents. However, these actions do not modify the actual value of the prop itself, as it remains a reference to an underlying structure.

An additional issue to note is that Vue is unable to detect modifications to Array elements or additions/deletions of Object members, as explained in this documentation.

For more information, check out this discussion on Stack Overflow.

Answer 3

Answer №2

To avoid potential issues, one approach is to create a shallow copy and assign it to a new data item within the child component.

Link to Example

var example = {
  props: ['exampleProp'],
  data: function() {
    return {
      myExample: this.exampleProp.slice()
    }
  },
  mounted: function() {
    this.myExample.push(10)
  },
  render: function() {}
}

new Vue({
  el: '#app',
  components: {
    'example': example
  },
  data: function() {
    return {
      newData: []
    }
  }
})

Answer 4

To avoid potential issues, one approach is to create a shallow copy and assign it to a new data item within the child component.

Link to Example

var example = {
  props: ['exampleProp'],
  data: function() {
    return {
      myExample: this.exampleProp.slice()
    }
  },
  mounted: function() {
    this.myExample.push(10)
  },
  render: function() {}
}

new Vue({
  el: '#app',
  components: {
    'example': example
  },
  data: function() {
    return {
      newData: []
    }
  }
})

Answer 5

Answer №3

It is recommended to avoid using the same name for both key and value

:datatest="dataTest" Incorrect Approach

:data-test="dataTest" Preferred Method (using Kabab case)

HTML

<div id="app">
  <span>Parent value: {{ dataTest }}</span>
  <test :data-test="dataTest" />
</div>

JS

var test = {
  props: {
        dataTest:{
        type:Number
      }
  },
  mounted: function() {
    this.datatest.push(10)
  },
  render: function() {}
}

new Vue({
  el: '#app',
  components: {
    'test': test
  },
  data: function() {
    return {
      dataTest: []
    }
  }
})

Output:

Parent value: []

Answer 6

It is recommended to avoid using the same name for both key and value

:datatest="dataTest" Incorrect Approach

:data-test="dataTest" Preferred Method (using Kabab case)

HTML

<div id="app">
  <span>Parent value: {{ dataTest }}</span>
  <test :data-test="dataTest" />
</div>

JS

var test = {
  props: {
        dataTest:{
        type:Number
      }
  },
  mounted: function() {
    this.datatest.push(10)
  },
  render: function() {}
}

new Vue({
  el: '#app',
  components: {
    'test': test
  },
  data: function() {
    return {
      dataTest: []
    }
  }
})

Output:

Parent value: []

Vue.js - Updating parent component from child component using one-way data binding

Answer №1

Answer №2

Answer №3

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