In my app user provides style codes inside input field. I want to add popup confirmation modal which will have message containing the number of provided style codes. I've got below:

<template>

<h4>Style number</h4>
<FormulateForm v-model="styleCodes">
      <FormulateInput
      name="product_codes"
      placeholder="Style number"
      />

      <button
        type="button"
        class="btn btn-primary"
        @click="syncProducts"
      >
        Sync
      </button>
</FormulateForm>

</template>

<script>

export default {
  name: 'SyncProducts',
  data() {
    return {
      styleCodes: [],
    }
  },
  computed: {
    productsToSyncAmount () {
      return this.styleCodes.length
    },
  methods: {
    async syncProducts() {
      let confirmationText = `Do you want to ${this.productsToSyncAmount} sync products?`

      if (this.productsToSyncAmount === 0) {
        ModalController.showToast('', 'Type product codes for sync first, please!', 'warning')
      }
      else if (await ModalController.showConfirmation('Confirmation', confirmationText)) {
        try {
          ModalController.showLoader()
          await createApparelMagicProductsRequest(this, this.styleCodes)
        } catch (data) {
          const errorMessage = `Error occurred during queueing products to sync - `
          ModalController.showToast('', errorMessage + data?.message, 'error')
        } finally {
          this.styleCodes = []
        }
      }
    },
  }
}
</script>

I think the crucial part is that one

  methods: {
    async syncProducts() {
      let confirmationText = `Do you want to ${this.productsToSyncAmount} sync products?`

I don't get it why this code produces undefined number from length and show me message Do you want to undefined sync products?. Inside the console I've got:

[Vue warn]: Invalid prop: type check failed for prop "formulateValue". Expected Object, got Array

How to fix that?