input框中出现提示文字（兼容ie 火狐 谷歌）

# HTML5 Placeholder jQuery Plugin ## Demo & Examples [http://mathiasbynens.be/demo/placeholder](http://mathiasbynens.be/demo/placeholder) ## Example Usage ### HTML ```html <input type="text" name="name" placeholder="e.g. John Doe"> <input type="email" name="email" placeholder="e.g. address@example.ext"> <input type="url" name="url" placeholder="e.g. http://mathiasbynens.be/"> <input type="tel" name="tel" placeholder="e.g. +32 472 77 69 88"> <input type="password" name="password" placeholder="e.g. h4x0rpr00fz"> <input type="search" name="search" placeholder="Search this site…"> <textarea name="message" placeholder="Your message goes here"></textarea> ``` ### jQuery Use the plugin as follows: ```js $('input, textarea').placeholder(); ``` You’ll still be able to use `jQuery#val()` to get and set the input values. If the element is currently showing a placeholder, `.val()` will return an empty string instead of the placeholder text, just like it does it browsers with a native `@placeholder` implementation. Calling `.val('')` to set an element’s value to the empty string will result in the placeholder text (re)appearing. ### CSS The plugin automatically adds `class="placeholder"` to the elements who are currently showing their placeholder text. You can use this to style placeholder text differently: ```css input, textarea { color: #000; } .placeholder { color: #aaa; } ``` I’d suggest sticking to the `#aaa` color for placeholder text, as it’s the default in most browsers that support `@placeholder`. If you really want to, though, you can [style the placeholder text in some of the browsers that natively support it](http://stackoverflow.com/questions/2610497/change-an-inputs-html5-placeholder-color-with-css/2610741#2610741). ## Notes * Requires jQuery 1.6+. For an older version of this plugin that works under jQuery 1.4.2+, see [v1.8.7](https://github.com/mathiasbynens/jquery-placeholder/tree/1.8.7). * Works in all A-grade browsers, including IE6. * Automatically checks if the browser natively supports the HTML5 `placeholder` attribute for `input` and `textarea` elements. If this is the case, the plugin won’t do anything. If `@placeholder` is only supported for `input` elements, the plugin will leave those alone and apply to `textarea`s exclusively. (This is the case for Safari 4, Opera 11.00, and possibly other browsers.) * Caches the results of its two feature tests in `jQuery.fn.placeholder.input` and `jQuery.fn.placeholder.textarea`. For example, if `@placeholder` is natively supported for `input` elements, `jQuery.fn.placeholder.input` will be `true`. After loading the plugin, you can re-use these properties in your own code. * Makes sure it never causes duplicate IDs in your DOM, even in browsers that need an extra `input` element to fake `@placeholder` for password inputs. This means you can safely do stuff like: ```html <label for="bar">Example label</label> <input type="password" placeholder="foo" id="bar"> ``` And the `<label>` will always point to the `<input>` element you’d expect. Also, all CSS styles based on the ID will just work™. ## License This plugin is dual licensed under the MIT and GPL licenses, just like jQuery itself. ## Thanks to… * [Paul Irish](http://paulirish.com/) for his inspiring snippet in [jQuery 1.4 Hawtness #1](http://jquery14.com/day-05/jquery-1-4-hawtness-1-with-paul-irish) * everyone from [#jquery](http://webchat.freenode.net/?channels=jquery) for the tips, ideas and patches * temp01 for his major contributions * anyone who [contributed a patch](https://github.com/mathiasbynens/jquery-placeholder/contributors) or [made a helpful suggestion](https://github.com/mathiasbynens/jquery-placeholder/issues) _– [Mathias](http://mathiasbynens.be/)_