选中时下拉标题更改

Question

我有以下代码，包含3个项目的2个ddls。是否可以将每个下拉列表中显示的标题更改为用户选择的任何项目，但仅使用vanilla JavaScript或CSS？任何事都会有所帮助，欢呼。

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 .dropbtn {
        background-color: #4CAF50;
        color: white;
        padding: 13px;
        font-size: 16px;
        width:125px;
        height:45px;
        border: none;
        cursor: pointer;
    }

    .dropdown {
        position: relative;
        display: inline-block;
    }

    .dropdown-content {
        display: none;
        position: absolute;
        background-color: #f9f9f9;
        min-width: 160px;
        box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
        z-index: 1;
    }

    .dropdown-content a {
        color: black;
        padding: 12px 16px;
        text-decoration: none;
        display: block;
    }

    .dropdown-content a:hover {background-color: #f1f1f1}

    .dropdown:hover .dropdown-content {
        display: block;
    }

    .dropdown:hover .dropbtn {
        background-color: #3e8e41;
    }

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 <div class="dropdown">
            <button class="dropbtn">Location</button>
      <div class="dropdown-content">
        <a href="#">Link 1</a>
        <a href="#">Link 2</a>
        <a href="#">Link 3</a>
      </div>
    </div>

    <div class="dropdown">
      <button class="dropbtn">Category</button>
      <div class="dropdown-content">
        <a href="#">Link 1</a>
        <a href="#">Link 2</a>
        <a href="#">Link 3</a>
      </div>
    </div>

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Answer 1

您可以使用select代替下拉列表，将第一个option设为selected和disabled，这样它只能用作按钮引用名称，但用户将无法使用选择它作为选项。

• <option value="none" selected disabled>Location</option>
• <option value="none" selected disabled>Category</option>

与当前下拉列表的唯一区别是悬停行为，您需要点击select，但可以使用CSS箭头轻松引用。

见下文：

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  -webkit-font-smoothing: antialiased;
  -moz-font-smoothing: antialiased;
  -o-font-smoothing: antialiased;
  font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

.container {
  width: 100%;
  margin: 0 auto;
  position: relative;
}

#contact input[type="text"],
#contact input[type="email"],
#contact input[type="tel"],
#contact textarea,
#contact button[type="submit"] {
  font: 400 12px/16px "Verdana", Verdana;
}

#contact {
  background: #F9F9F9;
  padding: 25px;
  box-shadow: 0 0 20px 0 rgba(0, 0, 0, 0.2), 0 5px 5px 0 rgba(0, 0, 0, 0.24);
  height: 477px;
}

#contact h3 {
  display: block;
  font-family: Verdana;
  font-size: 24px;
  font-weight: 300;
  margin-bottom: 10px;
}

#contact h4 {
  margin: 5px 0 15px;
  display: block;
  font-family: Verdana;
  font-size: 13px;
  font-weight: 400;
}

#contact h5 {
  text-decoration: underline;
  display: block;
  color: #4CAF50;
  font-family: Verdana;
  font-size: 19px;
  font-weight: normal;
  margin-bottom: 10px;
}

#contact h6 {
  text-decoration: underline;
  display: block;
  text-align: left;
  color: #4CAF50;
  font-family: Verdana;
  font-size: 15px;
  font-weight: normal;
  margin-bottom: 10px;
}

.fieldset {
  border: medium none !important;
  margin: 0 0 10px;
  min-width: 100%;
  padding: 0;
  width: 100%;
}

#contact input[type="text"],
#contact input[type="email"],
#contact input[type="tel"],
#contact textarea {
  width: 100%;
  border: 1px solid #ccc;
  background: #FFF;
  margin: 0 0 5px;
  padding: 10px;
}

#contact input[type="text"]:hover,
#contact input[type="email"]:hover,
#contact input[type="tel"]:hover,
#contact textarea:hover {
  -webkit-transition: border-color 0.3s ease-in-out;
  -moz-transition: border-color 0.3s ease-in-out;
  transition: border-color 0.3s ease-in-out;
  border: 1px solid #aaa;
}

#contact textarea {
  height: 100px;
  max-width: 100%;
  resize: none;
}

#button {
  float: right;
  cursor: pointer;
  padding: 13px 32px;
  width: 125px;
  height: 45px;
  border: none;
  font-family: Verdana;
  background: #4CAF50;
  color: #FFF;
  margin: 0 0 5px;
  font-size: 15px;
}

#button:hover {
  background: #43A047;
  -webkit-transition: background 0.3s ease-in-out;
  -moz-transition: background 0.3s ease-in-out;
  transition: background-color 0.3s ease-in-out;
}

#button:active {
  box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.5);
}

#contact input:focus,
#contact textarea:focus {
  outline: 0;
  border: 1px solid #aaa;
}

 ::-webkit-input-placeholder {
  color: #888;
}

 :-moz-placeholder {
  color: #888;
}

 ::-moz-placeholder {
  color: #888;
}

 :-ms-input-placeholder {
  color: #888;
}

.dropbtn {
  background-color: #4CAF50;
  color: white;
  padding: 13px;
  font-size: 16px;
  width: 125px;
  height: 45px;
  border: none;
  cursor: pointer;
}

/* new css */
select {
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
  border-radius: 0px;
  background-image: linear-gradient(45deg, transparent 50%, white 50%), linear-gradient(135deg, white 50%, transparent 50%), linear-gradient(to right, #ccc, #ccc);
  background-position: calc(100% - 20px) calc(1em + 5px), calc(100% - 15px) calc(1em + 5px), calc(100% - 2.5em) 0.5em;
  background-size: 5px 5px, 5px 5px, 0px 1.5em;
  background-repeat: no-repeat;
}
/* end new css */

.dropdown {
  position: relative;
  display: inline-block;
}

.dropdown-content {
  display: none;
  position: absolute;
  background-color: #f9f9f9;
  min-width: 160px;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
  z-index: 1;
}

.dropdown-content a {
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
}

.dropdown-content a:hover {
  background-color: #f1f1f1
}

.dropdown:hover .dropdown-content {
  display: block;
}

.dropdown:hover .dropbtn {
  background-color: #3e8e41;
}

input[type="file"] {
  display: none;
}

.custom-file-upload {
  cursor: pointer;
  padding: 13px 16px;
  width: 125px;
  height: 45px;
  border: none;
  font-family: Verdana;
  background: #4CAF50;
  color: #FFF;
  margin: 0 0 5px;
  font-size: 15px;
  display: inline-block;
  vertical-align: top;
  text-align: center;
}

.custom-file-upload:hover {
  background: #43A047;
  -webkit-transition: background 0.3s ease-in-out;
  -moz-transition: background 0.3s ease-in-out;
  transition: background-color 0.3s ease-in-out;
}

.custom-file-upload:active {
  box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.5);
}

.overlay {
  height: 477px;
  width: 0;
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  background-color: #F9F9F9;
  overflow-x: hidden;
  transition: 0.5s;
  padding-top: 25px;
  padding-bottom: 25px;
  padding-left: 25px;
  padding-right: 25px;
}

.overlay.collapsed {
  padding-top: 25px;
  padding-bottom: 25px;
  padding-left: 0;
  padding-right: 0;
}

.overlay-content {
  position: relative;
  /*top: 5%;*/
  width: 100%;
  height: 100%;
  text-align: center;
  /*margin-top: 25px;*/
}

.overlay-content .container {
  height: 100%;
}

.overlay-content fieldset:last-child {
  position: absolute;
  bottom: 0;
  margin-bottom: 0;
}

.overlay a {
  padding: 5px;
  margin-top: -15px;
  text-decoration: none;
  font-size: 36px;
  color: #818181;
  display: block;
  transition: 0.3s;
  z-index: 100;
}

.overlay a:hover,
.overlay a:focus {
  color: #bababa;
}

.overlay .closebtn {
  position: absolute;
  top: 15px;
  right: 15px;
  font-size: 40px;
}

@media screen and (max-height: 450px) {
  .overlay a {
    font-size: 20px
  }
  .overlay .closebtn {
    font-size: 40px;
    top: 15px;
    right: 35px;
  }
}

#contact-submit {
  float: right;
  cursor: pointer;
  font-size: 15px;
  padding: 13px 32px;
  width: 125px;
  height: 45px;
  border: none;
  font-family: Verdana;
  background: #4CAF50;
  color: #FFF;
  margin: 0 0 5px;
}

#contact-submit:hover {
  background: #43A047;
  -webkit-transition: background 0.3s ease-in-out;
  -moz-transition: background 0.3s ease-in-out;
  transition: background-color 0.3s ease-in-out;
}

#contact-submit:active {
  box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.5);
}

#label {
  float: left;
  text-decoration: underline;
  font-family: Verdana;
  font-size: 15px;
}

#labelDetail {
  padding-left: 25px;
  float: left;
  font-family: Verdana;
  font-size: 13px;
  text-align: left;
  max-height: 135px;
  overflow: auto;
}

#labelName {
  padding-left: 25px;
  float: left;
  font-family: Verdana;
  font-size: 13px;
}

#labelNumber {
  padding-left: 25px;
  float: left;
  font-family: Verdana;
  font-size: 13px;
}

#labelEmail {
  padding-left: 25px;
  float: left;
  font-family: Verdana;
  font-size: 13px;
}

#labelAttach {
  float: left;
  text-decoration: underline;
  font-family: Verdana;
  padding-top: 12px;
  color: #4CAF50;
}

#labelFile {
  float: left;
  font-family: Verdana;
  padding-top: 12px;
  padding-left: 5px;
}

#filename {
  font-family: Verdana;
  font-size: 10px;
  padding-top: 12px;
}

<div class="container">
  <form id="contact">
    <h3>Connect With HR</h3>
    <fieldset class="fieldset">
      <!-- HTML tweak -->
      <select class="dropbtn">
        <option value="none" selected disabled>Location</option>
        <option value="link1">Link 1</option>
        <option value="link2">Link 2</option>
        <option value="link3">Link 3</option>
      </select>
      <select class="dropbtn">
        <option value="none" selected disabled>Category</option>
        <option value="link1">Link 1</option>
        <option value="link2">Link 2</option>
        <option value="link3">Link 3</option>
      </select>
      <!-- end HTML tweak -->
    </fieldset>
    <fieldset class="fieldset">
      <textarea id="txtDetail" placeholder="Detail...." tabindex="2"></textarea>
    </fieldset>
    <h4>Contact Information</h4>
    <fieldset class="fieldset">
      <input id="txtName" placeholder="Name" type="text" tabindex="4">
      <input id="txtNumber" placeholder="Preferred Contact Number" type="tel" tabindex="5">
      <input id="txtEmail" placeholder="Preferred Email" type="email" tabindex="6">
    </fieldset>
    <fieldset class="fieldset">
      <label for="file-upload" class="custom-file-upload">
        <i class="fa fa-cloud-upload"></i> Attachment
    </label>
      <input id="file-upload" type="file" />
      <p id="filename" style="display: inline-block"></p>
      <div id="myNav" class="overlay collapsed">
        <a href="javascript:void(0)" class="closebtn" onclick="closeNav()">&times;</a>
        <div class="overlay-content">
          <div class="container">
            <h5>Summary</h5>
            <fieldset class="fieldset">
              <label id="label">Location:</label>
            </fieldset>
            <fieldset class="fieldset">
              <label id="label">Category:</label>
            </fieldset>
            <fieldset class="fieldset">
              <label id="label">Detail:</label>
              <label id="labelDetail"></label>
            </fieldset>
            <h6>Contact Information</h6>
            <fieldset class="fieldset">
              <label id="label">Name:</label>
              <label id="labelName"></label>
            </fieldset>
            <fieldset class="fieldset">
              <label id="label">Preferred Contact Number:</label>
              <label id="labelNumber"></label>
            </fieldset>
            <fieldset class="fieldset">
              <label id="label">Preferred Email:</label>
              <label id="labelEmail"></label>
            </fieldset>
            <fieldset class="fieldset">
              <label id="labelAttach">Attachment:</label>
              <label id="labelFile">File</label>
              <button name="submit" id="contact-submit" data-submit="...Sending">Submit</button>
            </fieldset>
          </div>
        </div>
      </div>
      <span id="button" onclick="openNav()">Preview</span>
    </fieldset>
  </form>
</div>