Vue Js Validate Phone Number

<body>
    <h3>Vue Js Validation of Indian Phone Numbers</h3>
    <div id="app">

<input type="text" v-model="phoneNumber" @input="validatePhoneNumber" />
        <pre v-if="phoneNumber">Phone Number Length {{phoneNumber.length}}</pre>
        <pre v-if="errorMessage" style="color:red">{{ errorMessage }}</pre>
    </div>
    <script type="module">
        const app = new Vue({
            el: "#app",
            data() {
                return {
                    phoneNumber: '',
                    errorMessage: ''
                };
            },
            methods: {
                validatePhoneNumber() {
                    const phoneNumber = this.phoneNumber;
                    const Regex = /^(?:(?:\+|0{0,2})91(\s*[\-]\s*)?|[0]?)?[6789]\d{9}$/;

if (this.phoneNumber === '') {
                        this.errorMessage = 'Phone Number field cannot be empty';
                    }

else if (!Regex.test(phoneNumber)) {
                        this.errorMessage = 'Invalid phone number';
                    }
                    else {
                        this.errorMessage = '';
                    }
                }
            }

})
    </script>
    <style>
        input[type="text"] {
            width: 250px;
            height: 40px;
            font-size: 16px;
            padding: 10px;
        }
    </style>

</body>

</html>