让低版本浏览器支持input的placeholder属性(js方法)

var doc = window.document, input = doc.createElement(input);
if( typeof input[placeholder] == undefined ) // 如果不支持placeholder属性
{
$(input).each(function( ele )
{
var me = $(this);
var ph = me.attr(placeholder);
if( ph && !me.val() )
{
me.val(ph).css(color, #aaa).css(line-height, me.css(height));
}
me.on(focus, function()
{
if( me.val() === ph)
{
me.val(null).css(color, );
}
}).on(blur, function()
{
if( !me.val() )
{
me.val(ph).css(color, #aaa).css(line-height, me.css(height));
}
});
});
}