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                <div class="col">
            <form action="">
              <span>mobile number:</span><br>
              <input type="text" type="number" name="mobileNumber" id="mobileNumber">
              <span>email address:</span><br>
              <input type="text" type="text" name="emailAddress" id="emailAddress">
            <button class="btn-default btn btn-primary" id="checkFormat">
              <span>check mobile & email format</span>


                $grey : #eee;

* {
  font-size: 18px;
.col {
  margin: auto;
  width: 90%;
  button {
    padding: 12px;
    margin: 10px 0 0 0;
    border-radius: 5px;
    cursor: pointer;
    background-color: $grey ;
    transition:.4s all ease;
      background-color: darken($grey,10%) ;

  input {
    display: block;
    width: 100%;
    margin: 10px 0;



                // 檢查手機號碼與電子郵件是否符合格式
let checkFormatBtn = document.getElementById("checkFormat");

  function checkFormat () {
    let mobileNumberVal = document.getElementById("mobileNumber").value;
    let emailAddressVal = document.getElementById("emailAddress").value;
    console.log(mobileNumberVal, emailAddressVal)
    let MobileNumRegex = /^0\d{9}/;
    let InputEmailRegex = /^\S+@\w+.\w{2,4}/;
    if (!MobileNumRegex.test(mobileNumber)) {
    } else {
      console.log("correct mobile format");
    if (!InputEmailRegex.test(emailAddress)) {
    } else {
      console.log("correct email format");