项目中使用的bootstrap，用到了placeholder属性，在IE8及IE8以下不显示
<input type="text" class="input-medium" placeholder="项目名称"/>
在网上找了一个基于jquery的插件，插件代码如下：
/*! http://mths.be/placeholder v2.0.7 by @mathias */
;(function(window, document, $) {
// Opera Mini v7 doesn’t support placeholder although its DOM seems to indicate so
var isOperaMini = Object.prototype.toString.call(window.operamini) == '[object OperaMini]';
var isInputSupported = 'placeholder' in document.createElement('input') && !isOperaMini;
var isTextareaSupported = 'placeholder' in document.createElement('textarea') && !isOperaMini;
var prototype = $.fn;
var valHooks = $.valHooks;
var propHooks = $.propHooks;
var hooks;
var placeholder;
if (isInputSupported && isTextareaSupported) {
placeholder = prototype.placeholder = function() {
return this;
};
placeholder.input = placeholder.textarea = true;
} else {
placeholder = prototype.placeholder = function() {
var $this = this;
$this
.filter((isInputSupported ? 'textarea' : ':input') + '[placeholder]')
.not('.placeholder')
.bind({
'focus.placeholder': clearPlaceholder,
'blur.placeholder': setPlaceholder
})
.data('placeholder-enabled', true)
.trigger('blur.placeholder');
return $this;
};
placeholder.input = isInputSupported;
placeholder.textarea = isTextareaSupported;
hooks = {
'get': function(element) {
var $element = $(element);
var $passwordInput = $element.data('placeholder-password');
if ($passwordInput) {
return $passwordInput[0].value;
}
return $element.data('placeholder-enabled') && $element.hasClass('placeholder') ? '' : element.value;
},
'set': function(element, value) {
var $element = $(element);
var $passwordInput = $element.data('placeholder-password');
if ($passwordInput) {
return $passwordInput[0].value = value;
}
if (!$element.data('placeholder-enabled')) {
return element.value = value;
}
if (value == '') {
element.value = value;
// Issue #56: Setting the placeholder causes problems if the element continues to have focus.
if (element != safeActiveElement()) {
// We can't use `triggerHandler` here because of dummy text/password inputs :(
setPlaceholder.call(element);
}
} else if ($element.hasClass('placeholder')) {
clearPlaceholder.call(element, true, value) || (element.value = value);
} else {
element.value = value;
}
// `set` can not return `undefined`; see http://jsapi.info/jquery/1.7.1/val#L2363
return $element;
}
};
if (!isInputSupported) {
valHooks.input = hooks;
propHooks.value = hooks;
}
if (!isTextareaSupported) {
valHooks.textarea = hooks;
propHooks.value = hooks;
}
$(function() {
// Look for forms
$(document).delegate('form', 'submit.placeholder', function() {
// Clear the placeholder values so they don't get submitted
var $inputs = $('.placeholder', this).each(clearPlaceholder);
setTimeout(function() {
$inputs.each(setPlaceholder);
}, 10);
});
});
// Clear placeholder values upon page reload
$(window).bind('beforeunload.placeholder', function() {
$('.placeholder').each(function() {
this.value = '';
});
});
}
function args(elem) {
// Return an object of element attributes
var newAttrs = {};
var rinlinejQuery = /^jQuery\d+$/;
$.each(elem.attributes, function(i, attr) {
if (attr.specified && !rinlinejQuery.test(attr.name)) {
newAttrs[attr.name] = attr.value;
}
});
return newAttrs;
}
function clearPlaceholder(event, value) {
var input = this;
var $input = $(input);
if (input.value == $input.attr('placeholder') && $input.hasClass('placeholder')) {
if ($input.data('placeholder-password')) {
$input = $input.hide().next().show().attr('id', $input.removeAttr('id').data('placeholder-id'));
// If `clearPlaceholder` was called from `$.valHooks.input.set`
if (event === true) {
return $input[0].value = value;
}
$input.focus();
} else {
input.value = '';
$input.removeClass('placeholder');
input == safeActiveElement() && input.select();
}
}
}
function setPlaceholder() {
var $replacement;
var input = this;
var $input = $(input);
var id = this.id;
if (input.value == '') {
if (input.type == 'password') {
if (!$input.data('placeholder-textinput')) {
try {
$replacement = $input.clone().attr({ 'type': 'text' });
} catch(e) {
$replacement = $('<input>').attr($.extend(args(this), { 'type': 'text' }));
}
$replacement
.removeAttr('name')
.data({
'placeholder-password': $input,
'placeholder-id': id
})
.bind('focus.placeholder', clearPlaceholder);
$input
.data({
'placeholder-textinput': $replacement,
'placeholder-id': id
})
.before($replacement);
}
$input = $input.removeAttr('id').hide().prev().attr('id', id).show();
// Note: `$input[0] != input` now!
}
$input.addClass('placeholder');
$input[0].value = $input.attr('placeholder');
} else {
$input.removeClass('placeholder');
}
}
function safeActiveElement() {
// Avoid IE9 `document.activeElement` of death
// https://github.com/mathiasbynens/jquery-placeholder/pull/99
try {
return document.activeElement;
} catch (err) {}
}
}(this, document, jQuery));
使用如下：
/**
* 让IE8，IE7等非HTML5的浏览器支持placeholder
*/
$(function() {
var v = 3, div = document.createElement('div'), all = div.getElementsByTagName('i');
while (
div.innerHTML = '<!--[if gt IE ' + (++v) + ']><i></i><![endif]-->',
all[0]
);
var ieflag= v > 4 ? v : false ;
if(ieflag){
$('input, textarea').placeholder();
var html;
if ($.fn.placeholder.input && $.fn.placeholder.textarea) {
html = '<strong>Your current browser natively supports <code>placeholder</code> for <code>input</code> and <code>textarea</code> elements.</strong> The plugin won’t run in this case, since it’s not needed. If you want to test the plugin, use an older browser ;)';
} else if ($.fn.placeholder.input) {
html = '<strong>Your current browser natively supports <code>placeholder</code> for <code>input</code> elements, but not for <code>textarea</code> elements.</strong> The plugin will only do its thang on the <code>textarea</code>s.';
}
if (html) {
$('<p class="note">' + html + '</p>').insertAfter('form');
}
}
});
