解决HTML5 placeholder的方案

来源:转载

使低版本浏览器支持Placeholder有很多方法,都不是很完美,或多或少有点问题,且有些原生支持的浏览器在获得焦点时会清空Placeholder提示。发现知乎网的解决方法不错,特记录下

windows系统中以下浏览器测试通过:Google Chrome 18,Firefox 12,IE 9,IE 6,Opera 11.5。在android 4.0系统也测试了下,原生浏览器及Opera Mobile12基本通过,缺陷是获得焦点时会清空Placeholder提示。

jquery.placeholder.zhihu.js部分:

 

 代码如下 复制代码    /*

    * html5 placeholder pollfill

    * - 使用绝对定位内嵌层

    * - 也适用于密码域

    * 目标浏览器: IE 6~9, FF 3.5

    ```

    // 默认

    $('input[placeholder]').placeholder()

 

    // autofocus 与 placeholder 搭配时,非 webkit 清空了提示文本,推荐

    $('input[placeholder]').placeholder({

      // 将删除原有 placehodler 属性,强制用 JS 实现替代       useNative: false,
      // focus 时不清除提示文本, keypress 有效字符时才清空
      hideOnFocus: false,
      // 附加样式
      style: {
        textShadow: 'none'
      }
    })
    ```
    */
    (function ($) {
      var attr = 'placeholder', nativeSupported = attr in document.createElement('input')
 
      $.fn.placeholder = function (options) {
        return this.each(function () {
          var $input = $(this)
 
          if ( typeof options === 'string' ) {
            options = { text: options }
          }
 
          var opt = $.extend({
            text     : '',
            style    : {},
            namespace: 'placeholder',
            useNative: true,
            hideOnFocus: true
          }, options || {})
 
          if ( !opt.text ) {
            opt.text = $input.attr(attr)
          }
 
          if (!opt.useNative) {
            $input.removeAttr(attr)
          }else if ( nativeSupported ) {
            // 仅改变文本
            $input.attr(attr, opt.text)
            return
          }
 
          var width     = $input.width(), height = $input.height()
          var box_style = ['marginTop', 'marginLeft', 'paddingTop', 'paddingLeft', 'paddingRight']
 
          var show      = function () { $layer.show() }
          var hide      = function () { $layer.hide() }
          var is_empty  = function () { return !$input.val() }
          var check     = function () { is_empty() ? show() : hide() }
 
          var position  = function () {
            var pos = $input.position()
            if (!opt.hideOnFocus) {
              // 按??藏的情况,需要移?庸?肆较袼
              pos.left += 2
            }
            $layer.css(pos)
            $.each(box_style, function (i, name) {
              $layer.css(name, $input.css(name))
            })
          }
 
          var layer_style = {
              color     : 'gray',
              cursor    : 'text',
              textAlign : 'left',
              position  : 'absolute',
              fontSize  : $input.css('fontSize'),
              fontFamily: $input.css('fontFamily'),
              display   : is_empty() ? 'block' : 'none'
          }
 
          // create
          var layer_props = {
            text  : opt.text,
            width : width,
            height: 'auto'
          }
 
          // 确保只绑定一次
          var ns = '.' + opt.namespace, $layer = $input.data('layer' + ns)
          if (!$layer) {
            $input.data('layer' + ns, $layer = $('<div>', layer_props).appendTo($input.offsetParent()) )
          }
 
          // activate
          $layer
          .css($.extend(layer_style, opt.style))
          .unbind('click' + ns)
          .bind('click' + ns, function () {
            opt.hideOnFocus && hide()
            $input.focus()
          })
 
          $input
          .unbind(ns)
          .bind('blur' + ns, check)
 
          if (opt.hideOnFocus) {
            $input.bind('focus' + ns, hide)
          }else{
            $input.bind('keypress keydown' + ns, function(e) {
              var key = e.keyCode
              if (e.charCode || (key >= 65 && key <=90)) {
                hide()
              }
            })
            .bind('keyup' + ns,check)
          }
 
          // 由于 ie 记住密码的特性,需要监听值改变
          // ie9 不支持 jq bind 此事件
          $input.get(0).onpropertychange = check
 
          position()
          check()
        })
      }
 
    })(jQuery)

html部分:

 代码如下 复制代码

 

    <!DOCTYPE html>
    <html lang="en">
    <head>
    <meta charset="utf-8">
    <!--[if lt IE 9]>
    <script src="js/html5shiv.js"></script>
    <![endif]-->
    <title>HTML5 placeholder jQuery Plugin</title>
    <style>
         body, input, textarea { font: 1em/1.4 Helvetica, Arial; }
         label code { cursor: pointer; float: left; width: 150px; }
         input { width: 14em; }
         textarea { height: 5em; width: 20em; }
         .placeholder { color: #aaa; }
         .note { border: 1px solid orange; padding: 1em; background: #ffffe0; }   
    </style>
    </head>
    <body>
         <h1>HTML5 Placeholder jQuery Plugin</h1>    
         <form id="test">
         <p><label><code>type=search</code> <input type="search" name="search" placeholder="Search this site…" autofocus></label></p>
         <p><label><code>type=text</code> <input type="text" name="name" placeholder="e.g. John Doe"></label></p>
         <p><label><code>type=email</code> <input type="email" name="email" placeholder="e.g. [email protected]"></label></p>
         <p><label><code>type=url</code> <input type="url" name="url" placeholder="e.g. http://mathiasbynens.be/"></label></p>
         <p><label><code>type=tel</code> <input type="tel" name="tel" placeholder="e.g. +32 472 77 69 88"></label></p>
         <p><label for="p"><code>type=password</code> </label><input type="password" name="password" placeholder="e.g. hunter2" id="p"></p>
         <p><label><code>textarea</code> <textarea name="message" placeholder="Your message goes here"></textarea></label></p>
         <p><input type="submit" value="type=submit"></p>
         </form>
         <script src="js/jquery-1.7.2.min.js"></script>    
         <script src="js/jquery.placeholder.zhihu.js"></script>
         <script>
              $(function(){              
                   var support = (function(input) {
                        return function(attr) { return attr in input }
                   })(document.createElement('input'))         
                   if ( !(support('placeholder') && $.browser.webkit) ) {              
                        $('input[placeholder],textarea[placeholder]').placeholder({
                             useNative: false, 
                             hideOnFocus: false, 
                             style: { 
                                  textShadow: 'none' 
                             } 
                        });
                   }
 
                   if ( !support('autofocus') ) {
                        $('input[autofocus]').focus()
                   }
              });
         </script>
    </body>
    </html>




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