How can I run a statement when modal close on vue?

My vue component like this :

<template>
    ...
    <b-modal ref="modal" id="modalInvoice" size="lg"  title="Invoice">
        <Invoice/>
        <div slot="modal-footer" class="w-100"> 
            <b-btn size="sm" class="float-right" variant="warning" @click="show=false">
                <i class="fa fa-print"></i> Print
            </b-btn>
        </div>
    </b-modal>

    ...
        <b-btn variant="warning" class="btn-square mt-2" v-b-modal.modalInvoice @click="checkout()"><i class="fa fa-credit-card-alt"></i>Checkout</b-btn>
    ...
</template>
<script>
    ...
    export default {
        ...
        mounted() {
            $(this.$refs.modal).on('hidden.bs.modal', () => {
                console.log('close modal')
            })
        },
    }
</script>

I try like that. So I try using ref="modal" and mounted. But it does not works. If modal close, the console.log is not show

How can I solve this problem?