js 判斷手機號格式

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 <form action="" method="post">
            <input type="text" value="" placeholder="您的姓名" name="name" required="required"  maxlength="20" />
            <input type="text" value="" placeholder="您的手機" name="tel" required="required" maxlength="11"
             id="phone" onblur="checkPhone()"/>
            <div style="clear:both"></div>
            <div id="" class='send'>
                <button type="submit" name="submit">提交</button>
            </div>
        </form>
        
        <iframe width="100%" height="300" src="https://c.runoob.com/iframe/5535" allowfullscreen="allowfullscreen" frameborder="0"></iframe>
        <script type="text/javascript">
            function checkPhone() {
                var phone = document.getElementById('phone').value;
                if (!(/^1(3|4|5|6|7|8|9)\d{9}$/.test(phone))) {
                    alert("手機號碼有誤，請重填");
                    return false;
                }
            }
        </script>