Force user enter phone number with only digits.
this.$phone_number = $(this.$elements.phone_number);
this.$phone_number.on('input', this.myHandler);
private myHandler = (): void => {
const phone_number = this.$phone_number.val() as string;
const digitRegex = new RegExp('^[0-9]*$');
const validPhoneNumber = digitRegex.test(phone_number);
if (phone_number.length > 0 && !validPhoneNumber) {
this.$phone_number.val(phone_number.slice(0, -1));
} else {
this.$phone_number.val(phone_number);
}
}