HTML5 placeholder disappears on focus

问题:

Is there a freely available jQuery plugin that changes placeholder behavior to match HTML5 spec?

Before Focus

On Focus Good (Safari)

On Focus Bad (Chrome, Firefox)

You can what your browser does with this simple fiddle.

HTML5 draft spec says:

User agents should present this hint to the user, after having stripped line breaks from it, when the element's value is the empty string and/or the control is not focused (e.g. by displaying it inside a blank unfocused control and hiding it otherwise).

The "/or" is new in current draft so I suppose that's why Chrome and Firefox don't support it yet. See WebKit bug #73629, Chromium bug #103025.

回答1:

Stefano J. Attardi wrote a nice jQuery plugin that just does that.
It is more stable than Robert's and also fades to a lighter grey when the field gets focused.

• See the demo page
• Grab it on GitHub
• Play with the fiddle

---

I modified his plugin to read placeholder attribute as opposed to manually creating a span.
This fiddle has complete code:

HTML

<input type="text" placeholder="Hello, world!">

JS

// Original code by Stefano J. Attardi, MIT license

(function($) {
    function toggleLabel() {
        var input = $(this);

        if (!input.parent().hasClass('placeholder')) {
            var label = $('<label>').addClass('placeholder');
            input.wrap(label);

            var span = $('<span>');
            span.text(input.attr('placeholder'))
            input.removeAttr('placeholder');
            span.insertBefore(input);
        }

        setTimeout(function() {
            var def = input.attr('title');
            if (!input.val() || (input.val() == def)) {
                input.prev('span').css('visibility', '');
                if (def) {
                    var dummy = $('<label></label>').text(def).css('visibility','hidden').appendTo('body');
                    input.prev('span').css('margin-left', dummy.width() + 3 + 'px');
                    dummy.remove();
                }
            } else {
                input.prev('span').css('visibility', 'hidden');
            }
        }, 0);
    };

    function resetField() {
        var def = $(this).attr('title');
        if (!$(this).val() || ($(this).val() == def)) {
            $(this).val(def);
            $(this).prev('span').css('visibility', '');
        }
    };

    var fields = $('input, textarea');

    fields.live('mouseup', toggleLabel); // needed for IE reset icon [X]
    fields.live('keydown', toggleLabel);
    fields.live('paste', toggleLabel);
    fields.live('focusin', function() {
        $(this).prev('span').css('color', '#ccc');
    });
    fields.live('focusout', function() {
        $(this).prev('span').css('color', '#999');
    });

    $(function() {
       $('input[placeholder], textarea[placeholder]').each(
           function() { toggleLabel.call(this); }
       );
    });

})(jQuery);

CSS

.placeholder {
  background: white;
  float: left;
  clear: both;
}
.placeholder span {
  position: absolute;
  padding: 5px;
  margin-left: 3px;
  color: #999;
}
.placeholder input, .placeholder textarea {
  position: relative;
  margin: 0;
  border-width: 1px;
  padding: 6px;
  background: transparent;
  font: inherit;
}

/* Hack to remove Safari's extra padding. Remove if you don't care about pixel-perfection. */
@media screen and (-webkit-min-device-pixel-ratio:0) {
    .placeholder input, .placeholder textarea { padding: 4px; }
}

回答2:

Robert Nyman discusses the problem and documents his approach in his blog.
This fiddle that has all the neccessary HTML, CSS and JS.

Unfortunately, he solves the problem by changing value.
This will not work by definition if placeholder text is itself a valid input.

回答3:

I found this question by googling out the solution to the same problem. It seems that existing plugins either don't work in elder browsers or hide placeholder on focus.

So I decided to roll on my own solution while trying to combine best parts from existing plugins.

You may check it out here and open an issue if you face any problems.

回答4:

How about something simple like this? On focus save out the placeholder attribute value and remove the attribute entirely; on blur, put the attribute back:

$('input[type="text"]').focus( function(){
  $(this).attr("data-placeholder",$(this).attr('placeholder')).removeAttr("placeholder");
});
$('input[type="text"]').blur( function(){
  $(this).attr("placeholder",$(this).attr('data-placeholder'));
});   

回答5:

I wrote my own css3 only solution. See if that fullfills all your needs.

http://codepen.io/fabiandarga/pen/MayNWm

This is my solution:

1. the input element is set to "required"
2. an aditional span element for the placeholder is needed. This element is moved on top of the input element (position: absolute;)
3. with css selectors the input element is tested for validity (required fields are invalid as long as there is no input) and the placeholder is then hidden.

Pitfall: The placeholder is blocking mouseevents to the input! This problem is circumvented by hiding the placeholder element when the mouse is inside the parent (wrapper).

<div class="wrapper">
  <input txpe="text" autofocus="autofocus" required/>
  <span class="placeholder">Hier text</span>
</div>

.placeholder {
  display: none;
  position: absolute;
  left: 0px;
  right: 0;
  top: 0px;
  color: #A1A1A1;
}
input:invalid + .placeholder {
  display: block;  /* show the placeholder as long as the "required" field is empty */
}
.wrapper:hover .placeholder {
  display: none; /* required to guarantee the input is clickable */
}

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

回答6:

Maybe you can try with Float Label Pattern :)

See Float labels in CSS