Can Vue recognize array changes using the Spread syntax?

Question

Can Vue recognize array changes using the Spread syntax?

According to Vue documentation:

Vue is unable to detect certain changes made to an array, such as:

Directly setting an item using the index, for example vm.items[indexOfItem] = newValue

Modifying the length of the array, like vm.items.length = newLength

However, there is no mention of how Vue handles spread operators.

If we use this.arr1 = [...arr2, ...arr3]; to assign values to arr1, which is initialized in data({}), will Vue be able to detect this change?

While spread operators can simplify tasks, are they considered safe for modifying arrays in this scenario?

javascript vue.js vuejs2 vue-component

Answer 1

Answer №1

When you update a reactive property with a new value, it remains reactive.

The way in which you create the new value is not as important as the actual assignment itself.

While Vue provides helpful array mutation methods like push and splice, it is advisable to treat all reactive properties as immutable - meaning, avoid direct modifications and always assign a fresh value.

Not Recommended (non-reactive)

this.arr[0].objectProperty = 'new value'
this.arr[0] = { 'new': 'value' }
this.arr.length = 0

Acceptable (supported by Vue)

this.arr.push({ 'new': 'value' })
this.arr.splice(0, 1)

Ideal Approach (Immutable)

this.arr = this.arr.filter(...)
this.arr = this.arr.concat(...)
this.arr = [...arr2, ...arr3]

This article focuses on React but the principles apply similarly to Vue (and other technologies utilizing Virtual DOM)

Immutability in React: There’s nothing wrong with mutating objects

Answer 2

When you update a reactive property with a new value, it remains reactive.

The way in which you create the new value is not as important as the actual assignment itself.

While Vue provides helpful array mutation methods like push and splice, it is advisable to treat all reactive properties as immutable - meaning, avoid direct modifications and always assign a fresh value.

Not Recommended (non-reactive)

this.arr[0].objectProperty = 'new value'
this.arr[0] = { 'new': 'value' }
this.arr.length = 0

Acceptable (supported by Vue)

this.arr.push({ 'new': 'value' })
this.arr.splice(0, 1)

Ideal Approach (Immutable)

this.arr = this.arr.filter(...)
this.arr = this.arr.concat(...)
this.arr = [...arr2, ...arr3]

This article focuses on React but the principles apply similarly to Vue (and other technologies utilizing Virtual DOM)

Immutability in React: There’s nothing wrong with mutating objects

Answer 3

Answer №2

Indeed, this method of data manipulation in Vue.js is both secure and efficient for handling data concatenation:

let app = new Vue({

  el: '#app',

  data() {
    return {
      arr1: [1, 2, 3],
      arr2: [4, 5, 6],
      arr3: []
    }
  },
  methods: {
    fillArray() {
      this.arr3 = [...this.arr1, ...this.arr2]
    },
    random() {
      this.arr3 = [...this.arr3, Number(Math.random() * 100).toFixed()]
    },
    updateFirstIndex() {
      this.arr3[0] = 44;
      console.log(this.arr3);
    }
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <button @click="fillArray">
    Fill the array
</button>
  <button @click="random">
    Add a random value
</button>
<br>
It should be noted that reactivity might not occur if you directly update an element at a specific index:

  <button @click="updateFirstIndex">
  Update First Index
</button>
  <pre>
{{arr3}}
</pre>
</div>

Answer 4

Indeed, this method of data manipulation in Vue.js is both secure and efficient for handling data concatenation:

let app = new Vue({

  el: '#app',

  data() {
    return {
      arr1: [1, 2, 3],
      arr2: [4, 5, 6],
      arr3: []
    }
  },
  methods: {
    fillArray() {
      this.arr3 = [...this.arr1, ...this.arr2]
    },
    random() {
      this.arr3 = [...this.arr3, Number(Math.random() * 100).toFixed()]
    },
    updateFirstIndex() {
      this.arr3[0] = 44;
      console.log(this.arr3);
    }
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <button @click="fillArray">
    Fill the array
</button>
  <button @click="random">
    Add a random value
</button>
<br>
It should be noted that reactivity might not occur if you directly update an element at a specific index:

  <button @click="updateFirstIndex">
  Update First Index
</button>
  <pre>
{{arr3}}
</pre>
</div>

Can Vue recognize array changes using the Spread syntax?

Answer №1

Not Recommended (non-reactive)

Acceptable (supported by Vue)

Ideal Approach (Immutable)

Answer №2

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