javascript - How do I push items into an array in the data object in Vuejs? Vue seems not to be watching the .push() method - St

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I am attempting to add objects into an array I declared in Vue instance data object. I can set the values in the state's purchase object, but when I push data into the orders queue array, the empty array is not populated. The function is being triggered, but the array does not update.

Here is my form:

<form
  v-on:submit.prevent="queuePurchase"
  class="form-inline row"
  id="order-creation-form"
  method="POST"
>

  @csrf
  <autocomplete-field
    sizing="col-xs-12 col-sm-3 col-md-3"
    name="customer"
    label="Customer"
    :data="{{ json_encode($customers) }}"
    v-on:setcustomer="setCustomer($event)"
  ></autocomplete-field>

  <div class="col-xs-12 col-sm-3 col-md3 form-group d-flex flex-column align-items-start">
    <label for="phone">Product</label>
    <select
      v-model="purchase.product"
      class="form-control w-100"
      name="product"
      aria-describedby="productHelpBlock"
      required
    >
      @foreach ($products as $product)
        <option :value="{{ json_encode($product) }}">
          {{ $product->name }}
        </option>
      @endforeach
    </select>
    <small id="productHelpBlock" class="form-text text-muted">
      Select a product
    </small>
  </div>

  <div class="col-xs-12 col-sm-3 col-md-3 form-group d-flex flex-column align-items-start">
    <label for="phone">Quantity</label>
    <input
      v-model="purchase.quantity"
      type="number"
      min="1"
      name="product"
      class="form-control w-100"
      aria-describedby="productHelpBlock"
      required
    >
    <small id="productHelpBlock" class="form-text text-muted">
      Product quantity
    </small>
  </div>

  <div class="form-group">
    <button type="submit" class="btn btn-success icon-button d-flex">
      <i class="material-icons">add</i>
      <span>&nbsp;&nbsp;  Q U E U E</span>
    </button>
  </div>
</form>

And here is my javascript:

require("./bootstrap");
window.Vue = require("vue");

Vueponent("queue-table", require('./components/QueueTable.vue'));
Vueponent("autocomplete-field", require('./components/AutocompleteField.vue'));

const purchaseApp = new Vue({
    el: "#purchase-app",

    data() {
        return {
            queue: [],
            purchase: {
                product: null,
                customer: null,
                quantity: null
            }
        }
    },

    methods: {
        setCustomer: function(customerObj) {
            this.purchase.customer = customerObj;
        },

        queuePurchase: function() {
            this.queue.push( this.purchase );
        }
    }
});

Could someone please explain what & why it is happening?

I am attempting to add objects into an array I declared in Vue instance data object. I can set the values in the state's purchase object, but when I push data into the orders queue array, the empty array is not populated. The function is being triggered, but the array does not update.

Here is my form:

<form
  v-on:submit.prevent="queuePurchase"
  class="form-inline row"
  id="order-creation-form"
  method="POST"
>

  @csrf
  <autocomplete-field
    sizing="col-xs-12 col-sm-3 col-md-3"
    name="customer"
    label="Customer"
    :data="{{ json_encode($customers) }}"
    v-on:setcustomer="setCustomer($event)"
  ></autocomplete-field>

  <div class="col-xs-12 col-sm-3 col-md3 form-group d-flex flex-column align-items-start">
    <label for="phone">Product</label>
    <select
      v-model="purchase.product"
      class="form-control w-100"
      name="product"
      aria-describedby="productHelpBlock"
      required
    >
      @foreach ($products as $product)
        <option :value="{{ json_encode($product) }}">
          {{ $product->name }}
        </option>
      @endforeach
    </select>
    <small id="productHelpBlock" class="form-text text-muted">
      Select a product
    </small>
  </div>

  <div class="col-xs-12 col-sm-3 col-md-3 form-group d-flex flex-column align-items-start">
    <label for="phone">Quantity</label>
    <input
      v-model="purchase.quantity"
      type="number"
      min="1"
      name="product"
      class="form-control w-100"
      aria-describedby="productHelpBlock"
      required
    >
    <small id="productHelpBlock" class="form-text text-muted">
      Product quantity
    </small>
  </div>

  <div class="form-group">
    <button type="submit" class="btn btn-success icon-button d-flex">
      <i class="material-icons">add</i>
      <span>&nbsp;&nbsp;  Q U E U E</span>
    </button>
  </div>
</form>

And here is my javascript:

require("./bootstrap");
window.Vue = require("vue");

Vue.component("queue-table", require('./components/QueueTable.vue'));
Vue.component("autocomplete-field", require('./components/AutocompleteField.vue'));

const purchaseApp = new Vue({
    el: "#purchase-app",

    data() {
        return {
            queue: [],
            purchase: {
                product: null,
                customer: null,
                quantity: null
            }
        }
    },

    methods: {
        setCustomer: function(customerObj) {
            this.purchase.customer = customerObj;
        },

        queuePurchase: function() {
            this.queue.push( this.purchase );
        }
    }
});

Could someone please explain what & why it is happening?

• javascript
• laravel-5
• vue.js
• vuejs2
• vue-reactivity

Share Improve this question Follow edited Sep 8, 2018 at 21:52 Travis Hohl 2,19622 gold badges1515 silver badges1515 bronze badges asked Sep 8, 2018 at 13:33 user4998157user4998157 5

• you can read about reactivity in vue here vuejs.org/v2/guide/list.html#Caveats – Chris Li Commented Sep 8, 2018 at 13:37
• @ChrisLi .push() should be covered according to this vuejs.org/v2/guide/list.html#Mutation-Methods – user4998157 Commented Sep 8, 2018 at 13:48
• 1 This should work. You probably want to copy the purchase objects though before you push them to queue. Objects are reference types. So your queue will always store the same reference (which points to this.purchase). – FK82 Commented Sep 8, 2018 at 14:09
• where do you display the queue ? – Roland Commented Sep 8, 2018 at 14:24
• you had set :data="{{ json_encode($customers) }}" i think you can't do that, probably you can do :customers="{{ json_encode($customers) }}" and in your data object set ` data() { return { customers :[] ...` – Boussadjra Brahim Commented Sep 8, 2018 at 14:24

Add a comment  | 

1 Answer 1

Sorted by: Reset to default 18

The push() method ought to add purchase objects to the queue array, but as @FK82 pointed out in his comment, push() is adding multiple references to the same purchase object. This means that if you change the object by increasing the quantity, every purchase's quantity property will be updated.

You can give that a try here:

const exampleComponent = Vue.component("example-component", {
  name: "exampleComponent",
  template: "#example-component",
  data() {
    return {
      queue: [],
      purchase: {
        product: null,
        customer: null,
        quantity: null
      }
    };
  },
  methods: {
    queuePurchase() {
      this.queue.push( this.purchase );
    }
  }
});

const page = new Vue({
  name: "page",
  el: ".page",
  components: {
    "example-component": exampleComponent
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.2.4/vue.min.js"></script>
<template id="example-component">
  <div>
    <p>The Queue has {{ this.queue.length }} items.</p>
    <input
      v-model="purchase.quantity"
      type="number"
      min="1"
      name="product"
      placeholder="Quantity"
    >
    <button @click="queuePurchase">
      Add to Queue
    </button>
    <pre>{{ JSON.stringify(this.queue, null, 2) }}</pre>
  </div>
</template>

<div class="page">
  <example-component></example-component>
</div>

Instead of push()ing a reference to the same purchase object, try creating a shallow copy with Object.assign({}, this.purchase) or by using the spread operator. Here's an example that uses the spread operator and then push()es the copy onto the queue:

const exampleComponent = Vue.component("example-component", {
  name: "exampleComponent",
  template: "#example-component",
  data() {
    return {
      queue: [],
      purchase: {
        product: null,
        customer: null,
        quantity: null
      }
    };
  },
  methods: {
    queuePurchase() {
      this.queue.push({...this.purchase});
    }
  }
});

const page = new Vue({
  name: "page",
  el: ".page",
  components: {
    "example-component": exampleComponent
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.2.4/vue.min.js"></script>
<template id="example-component">
  <div>
    <p>The Queue has {{ this.queue.length }} items.</p>
    <input
      v-model="purchase.quantity"
      type="number"
      min="1"
      name="product"
      placeholder="Quantity"
    >
    <button @click="queuePurchase">
      Add to Queue
    </button>
    <pre>{{ JSON.stringify(this.queue, null, 2) }}</pre>
  </div>
</template>

<div class="page">
  <example-component></example-component>
</div>

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