How do I make a placeholder for a 'select'

2018-12-31 03:08发布

I'm using placeholders for text inputs which is working out just fine. But I'd like to use a placeholder for my selectboxes as well. Ofcourse I can just use this code:

<select>
    <option value="">Select your option</option>
    <option value="hurr">Durr</option>
</select>

But the 'Select your option' is in black instead of lightgrey. So my solution could possibly be CSS-based. jQuery is fine too.

This only makes the option grey in the dropdown (so after clicking the arrow):

option:first {
    color: #999;
}

Edit: The question is: how do people create placeholders in selectboxes? But it has already been answered, cheers.

And using this results in the selected value always being grey (even after selecting a real option):

select {
    color:#999;
}

23条回答
其实,你不懂
2楼-- · 2018-12-31 03:30

here is mine

select:focus option.holder {
  display: none;
}
<select>
    <option selected="selected" class="holder">Please select</option>
    <option value="1">Option #1</option>
    <option value="2">Option #2</option>

</select>

查看更多
还给你的自由
3楼-- · 2018-12-31 03:31

I'm not content with HTML/CSS only solutions, so I've decided to create a custom select using JS.

This is something I've written in the past 30 mins, thus it can be further improved.

All you have to do is create a simple list with few data attributes. The code automatically turns the list into a selectable dropdown. It also adds a hidden input to hold the selected value, so it can be used in a form.

Input:

<ul class="select" data-placeholder="Role" data-name="role">
  <li data-value="admin">Administrator</li>
  <li data-value="mod">Moderator</li>
  <li data-value="user">User</li>
</ul>

Output:

<div class="ul-select-container">
    <input type="hidden" name="role" class="hidden">
    <div class="selected placeholder">
        <span class="text">Role</span>
        <span class="icon">▼</span>
    </div>
    <ul class="select" data-placeholder="Role" data-name="role">
        <li class="placeholder">Role</li>
        <li data-value="admin">Administrator</li>
        <li data-value="mod">Moderator</li>
        <li data-value="user">User</li>
    </ul>
</div>

The text of the item that's supposed to be a placeholder is grayed out. The placeholder is selectable, in case the user wants to revert his/her choice. Also using CSS, all the drawbacks of select can be overcome (e.g., inability of the styling of the options).

// helper function to create elements faster/easier
// https://github.com/akinuri/js-lib/blob/master/element.js
var elem = function(tagName, attributes, children, isHTML) {
  let parent;
  if (typeof tagName == "string") {
    parent = document.createElement(tagName);
  } else if (tagName instanceof HTMLElement) {
    parent = tagName;
  }
  if (attributes) {
    for (let attribute in attributes) {
      parent.setAttribute(attribute, attributes[attribute]);
    }
  }
  var isHTML = isHTML || null;
  if (children || children == 0) {
    elem.append(parent, children, isHTML);
  }
  return parent;
};
elem.append = function(parent, children, isHTML) {
  if (parent instanceof HTMLTextAreaElement || parent instanceof HTMLInputElement) {
    if (children instanceof Text || typeof children == "string" || typeof children == "number") {
      parent.value = children;
    } else if (children instanceof Array) {
      children.forEach(function(child) {
        elem.append(parent, child);
      });
    } else if (typeof children == "function") {
      elem.append(parent, children());
    }
  } else {
    if (children instanceof HTMLElement || children instanceof Text) {
      parent.appendChild(children);
    } else if (typeof children == "string" || typeof children == "number") {
      if (isHTML) {
        parent.innerHTML += children;
      } else {
        parent.appendChild(document.createTextNode(children));
      }
    } else if (children instanceof Array) {
      children.forEach(function(child) {
        elem.append(parent, child);
      });
    } else if (typeof children == "function") {
      elem.append(parent, children());
    }
  }
};


// initialize all selects on the page
$("ul.select").each(function() {
  var parent    = this.parentElement;
  var refElem   = this.nextElementSibling;
  var container = elem("div", {"class": "ul-select-container"});
  var hidden    = elem("input", {"type": "hidden", "name": this.dataset.name, "class": "hidden"});
  var selected  = elem("div", {"class": "selected placeholder"}, [
    elem("span", {"class": "text"}, this.dataset.placeholder),
    elem("span", {"class": "icon"}, "&#9660;", true),
  ]);
  var placeholder = elem("li", {"class": "placeholder"}, this.dataset.placeholder);
  this.insertBefore(placeholder, this.children[0]);
  container.appendChild(hidden);
  container.appendChild(selected);
  container.appendChild(this);
  parent.insertBefore(container, refElem);
});

// update necessary elements with the selected option
$(".ul-select-container ul li").on("click", function() {
  var text     = this.innerText;
  var value    = this.dataset.value || "";
  var selected = this.parentElement.previousElementSibling;
  var hidden   = selected.previousElementSibling;
  hidden.value = selected.dataset.value = value;
  selected.children[0].innerText = text;
  if (this.classList.contains("placeholder")) {
    selected.classList.add("placeholder");
  } else {
    selected.classList.remove("placeholder");
  }
  selected.parentElement.classList.remove("visible");
});

// open select dropdown
$(".ul-select-container .selected").on("click", function() {
  if (this.parentElement.classList.contains("visible")) {
    this.parentElement.classList.remove("visible");
  } else {
    this.parentElement.classList.add("visible");
  }
});

// close select when focus is lost
$(document).on("click", function(e) {
  var container = $(e.target).closest(".ul-select-container");
  if (container.length == 0) {
    $(".ul-select-container.visible").removeClass("visible");
  }
});
.ul-select-container {
  width: 200px;
  display: table;
  position: relative;
  margin: 1em 0;
}
.ul-select-container.visible ul {
  display: block;
  padding: 0;
  list-style: none;
  margin: 0;
}
.ul-select-container ul {
  background-color: white;
  border: 1px solid hsla(0, 0%, 60%);
  border-top: none;
  -webkit-user-select: none;
  display: none;
  position: absolute;
  width: 100%;
  z-index: 999;
}
.ul-select-container ul li {
  padding: 2px 5px;
}
.ul-select-container ul li.placeholder {
  opacity: 0.5;
}
.ul-select-container ul li:hover {
  background-color: dodgerblue;
  color: white;
}
.ul-select-container ul li.placeholder:hover {
  background-color: rgba(0, 0, 0, .1);
  color: initial;
}
.ul-select-container .selected {
  background-color: white;
  padding: 3px 10px 4px;
  padding: 2px 5px;
  border: 1px solid hsla(0, 0%, 60%);
  -webkit-user-select: none;
}
.ul-select-container .selected {
  display: flex;
  justify-content: space-between;
}
.ul-select-container .selected.placeholder .text {
  color: rgba(0, 0, 0, .5);
}
.ul-select-container .selected .icon {
  font-size: .7em;
  display: flex;
  align-items: center;
  opacity: 0.8;
}
.ul-select-container:hover .selected {
  border: 1px solid hsla(0, 0%, 30%);
}
.ul-select-container:hover .selected .icon {
  opacity: 1;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<ul class="select" data-placeholder="Role" data-name="role">
  <li data-value="admin">Administrator</li>
  <li data-value="mod">Moderator</li>
  <li data-value="user">User</li>
</ul>

<ul class="select" data-placeholder="Sex" data-name="sex">
  <li data-value="male">Male</li>
  <li data-value="female">Female</li>
</ul>


Update: I've improved this (selection using up/down/enter keys). Tidied up the output a little bit and turned this into a object. Current output:

<div class="li-select-container">
    <input type="text" readonly="" placeholder="Role" title="Role">
    <span class="arrow">▼</span>
    <ul class="select">
        <li class="placeholder">Role</li>
        <li data-value="admin">Administrator</li>
        <li data-value="mod">Moderator</li>
        <li data-value="user">User</li>
    </ul>
</div>

Initialization:

new Liselect(document.getElementsByTagName("ul")[0]);

For further examination: JSFiddle, GitHub (renamed).


Update: Rewritten this again. Instead of using a list, we can just use a select. This way it'll work even without JS (in case it's disabled).

Input:

<select name="role" data-placeholder="Role" required title="Role">
    <option value="admin">Administrator</option>
    <option value="mod">Moderator</option>
    <option>User</option>
</select>

new Advancelect(document.getElementsByTagName("select")[0]);

Output:

<div class="advanced-select">
    <input type="text" readonly="" placeholder="Role" title="Role" required="" name="role">
    <span class="arrow">▼</span>
    <ul>
        <li class="placeholder">Role</li>
        <li data-value="admin">Administrator</li>
        <li data-value="mod">Moderator</li>
        <li>User</li>
    </ul>
</div>

JSFiddle, GitHub.

查看更多
荒废的爱情
4楼-- · 2018-12-31 03:33

Another possibility in JS:

 $('body').on('change','select', function (ev){
    if($(this).find('option:selected').val() == ""){
        $(this).css('color','#999');
        $(this).children().css('color','black');
    }
    else {
        $(this).css('color','black');
        $(this).children().css('color','black');
    }
});

JSFiddle

查看更多
情到深处是孤独
5楼-- · 2018-12-31 03:33

You can do this without using Javascript using only HTML You need to set default select option disabled="" and selected="" and select tag required="". Browser doesn't allow user to submit the form without selecting an option.

<form action="" method="POST">
    <select name="in-op" required="">
        <option disabled="" selected="">Select Option</option>
        <option>Option 1</option>
        <option>Option 2</option>
        <option>Option 3</option>
    </select>
    <input type="submit" value="Submit">
</form>
查看更多
看淡一切
6楼-- · 2018-12-31 03:34

Input [type="text"] Style Placeholder for Select Elements

The following solution simulates a placeholder as it relates to an input[type="text"] element:

$('.example').change(function () {
  $(this).css('color', $(this).val() === '' ? '#999' : '#555');
});
.example {
  color: #999;
}

.example > option {
  color: #555;
}

.example > option[value=""] {
  color: #999;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<select class="example">
  <option value="">Select Option</option>
  <option>Option 1</option>
  <option>Option 2</option>
  <option>Option 3</option>
</select>

查看更多
几人难应
7楼-- · 2018-12-31 03:35

Just stumbled across this question, here's what works in FireFox & Chrome (at least)

<style>
    select:invalid { color: gray; }
</style>
<form>
    <select required>
        <option value="" disabled selected hidden>Please Choose...</option>
        <option value="0">Open when powered (most valves do this)</option>
        <option value="1">Closed when powered, auto-opens when power is cut</option>
    </select>
</form>

The Disabled option stops the <option> being selected with both mouse and keyboard, whereas just using 'display:none' allows the user to still select via the keyboard arrows. The 'display:none' style just makes the list box look 'nice'.

Note: Using an empty value attribute on the "placeholder" option allows validation (required attribute) to work around having the "placeholder", so if the option isn't changed but is required; the browser should prompt the user to choose an option from the list.

Update (July 2015):

This method is confirmed working in the following browsers:

  • Google Chrome - v.43.0.2357.132
  • Mozilla Firefox - v.39.0
  • Safari - v.8.0.7 (Placeholder is visible in dropdown but is not selectable)
  • Microsoft Internet Explorer - v.11 (Placeholder is visible in dropdown but is not selectable)
  • Project Spartan - v.15.10130 (Placeholder is visible in dropdown but is not selectable)

Update (October 2015):

Removed the style="display: none" in favour of HTML5 attribute hidden which has wide support. The hidden element has similar traits as display: none in Safari, IE, (Project Spartan needs checking) where the option is visible in dropdown but is not selectable.

Update (January 2016):

When the select element is required it allows use of the :invalid CSS pseudo-class which allows you to style the select element when in it's "placeholder" state. :invalid works here because of the empty value in the placeholder option.

Once a value has been set the :invalid pseudo-class will be dropped. You can optionally also use :valid if you so wish.

Most browsers support this pseudo-class. IE10+. This works best with custom styled select elements; In some cases i.e. ( Mac in Chrome / Safari) you'll need to change the default appearance of the select box so that certain styles display i.e. background-color, color. You can find some examples and more about compatibility at developer.mozilla.org.

Native element appearance Mac in Chrome:

Select box native Mac in Chrome

Using altered border element Mac in Chrome:

Altered select box Mac in Chrome

查看更多
登录 后发表回答