When working with an array of objects in Vue.js, what is the optimal approach: replacing the entire array or modifying individual values?

Question

When working with an array of objects in Vue.js, what is the optimal approach: replacing the entire array or modifying individual values?

I am currently utilizing Vue and Vuex to dynamically generate components from an array retrieved from SQLite using the library better-sqlite3.

let table=[
  {
    id:1,
    column_1:'data',
    column_2:'data',
    column_3:{'1':'data','2':'data','3':'data'}
  },
  {
    id:2,
    column_1:'data',
    column_2:'data',
    column_3:{'1':'data','2':'data','3':'data'}
  },
  ...
]

In certain scenarios, it is necessary to update the data of multiple rows simultaneously. Considering the need to exchange data between SQLite and Vue, I am contemplating whether updating the data with SQL and then replacing the entire JavaScript array with the updated information, including the unaltered rows, would be a simpler and safe approach. Alternatively, I could iterate through the array using .find() to pinpoint and modify specific items. Therefore, my inquiry revolves around whether substituting the complete array is detrimental in terms of reactivity or if Vue can intelligently handle updates.

javascript vue.js vuejs2 better-sqlite3

Answer 1

Answer №1

Vue has a unique approach to monitoring UI updates.

Vue utilizes getters/setters on the data object for tracking mutations. When you trigger this.table = [{}, {}, {}, ...];, it will pass through the setter of table. Within the setter, there is a mechanism to inform the watcher and add these data changes to a queue.

Restrictions/Behavior when modifying Arrays:

Vue is unable to detect the following modifications within an array:

Directly setting an item using its index, e.g., vm.items[indexOfItem] = newValue
Altering the length of the array, e.g., vm.items.length = newLength

Illustration based on the above two statements:

const app = new Vue({
  el: '#app',
  data() {
    return {
      table: [{
        id: 1,
        column_1: 'data1',
        column_2: 'data',
        column_3: {'1': 'data', '2': 'data', '3': 'data'}
      }, {
        id: 2,
        column_1: 'data2',
        column_2: 'data',
        column_3: {'1': 'data', '2': 'data', '3': 'data'}
      }]
    }
  },
  mounted() {
    // Updating a specific array item does not trigger reactivity (The UI remains unchanged)
    this.table[1] = {
      id: 3,
      column_1: 'data3',
      column_2: 'data',
      column_3: {'1': 'data', '2': 'data', '3': 'data'}
    }
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <ul>
    <li v-for="item in table" :key="item.id">
      {{ item.column_1 }}
    </li>
  </ul>
</div>

Your Question's Answer: Keeping in mind the above points, one must update the entire array including unaltered rows for proper detection of changes.

Exemplification of the answer to your question:

const app = new Vue({
  el: '#app',
  data() {
    return {
      table: [{
        id: 1,
        column_1: 'data1',
        column_2: 'data',
        column_3: {'1': 'data', '2': 'data', '3': 'data'}
      }, {
        id: 2,
        column_1: 'data2',
        column_2: 'data',
        column_3: {'1': 'data', '2': 'data', '3': 'data'}
      }]
    }
  },
  mounted() {
    // Updating the entire array triggers reactivity (UI updates accordingly)
    this.table = [{
      id: 1,
      column_1: 'data1',
      column_2: 'data',
      column_3: {'1': 'data', '2': 'data', '3': 'data'}
    }, {
      id: 3,
      column_1: 'data3',
      column_2: 'data',
      column_3: {'1': 'data', '2': 'data', '3': 'data'}
    }]
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <ul>
    <li v-for="item in table" :key="item.id">
      {{ item.column_1 }}
    </li>
  </ul>
</div>

Answer 2

Vue has a unique approach to monitoring UI updates.

Vue utilizes getters/setters on the data object for tracking mutations. When you trigger this.table = [{}, {}, {}, ...];, it will pass through the setter of table. Within the setter, there is a mechanism to inform the watcher and add these data changes to a queue.

Restrictions/Behavior when modifying Arrays:

Vue is unable to detect the following modifications within an array:

Directly setting an item using its index, e.g., vm.items[indexOfItem] = newValue
Altering the length of the array, e.g., vm.items.length = newLength

Illustration based on the above two statements:

const app = new Vue({
  el: '#app',
  data() {
    return {
      table: [{
        id: 1,
        column_1: 'data1',
        column_2: 'data',
        column_3: {'1': 'data', '2': 'data', '3': 'data'}
      }, {
        id: 2,
        column_1: 'data2',
        column_2: 'data',
        column_3: {'1': 'data', '2': 'data', '3': 'data'}
      }]
    }
  },
  mounted() {
    // Updating a specific array item does not trigger reactivity (The UI remains unchanged)
    this.table[1] = {
      id: 3,
      column_1: 'data3',
      column_2: 'data',
      column_3: {'1': 'data', '2': 'data', '3': 'data'}
    }
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <ul>
    <li v-for="item in table" :key="item.id">
      {{ item.column_1 }}
    </li>
  </ul>
</div>

Your Question's Answer: Keeping in mind the above points, one must update the entire array including unaltered rows for proper detection of changes.

Exemplification of the answer to your question:

const app = new Vue({
  el: '#app',
  data() {
    return {
      table: [{
        id: 1,
        column_1: 'data1',
        column_2: 'data',
        column_3: {'1': 'data', '2': 'data', '3': 'data'}
      }, {
        id: 2,
        column_1: 'data2',
        column_2: 'data',
        column_3: {'1': 'data', '2': 'data', '3': 'data'}
      }]
    }
  },
  mounted() {
    // Updating the entire array triggers reactivity (UI updates accordingly)
    this.table = [{
      id: 1,
      column_1: 'data1',
      column_2: 'data',
      column_3: {'1': 'data', '2': 'data', '3': 'data'}
    }, {
      id: 3,
      column_1: 'data3',
      column_2: 'data',
      column_3: {'1': 'data', '2': 'data', '3': 'data'}
    }]
  }
})

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <ul>
    <li v-for="item in table" :key="item.id">
      {{ item.column_1 }}
    </li>
  </ul>
</div>

When working with an array of objects in Vue.js, what is the optimal approach: replacing the entire array or modifying individual values?

Answer №1

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