jQuery-placeholder

function isPlaceholder(){
    var input = document.createElement('input');
    return 'placeholder' in input;
}
if (!isPlaceholder()) {//不支持placeholder 用jquery来完成
    $(document).ready(function() {
        if(!isPlaceholder()){
            $("input").not("input[type='password']").each(//把input绑定事件 排除password框
                function(){
                    if($(this).val()=="" && $(this).attr("placeholder")!=""){
                        $(this).val($(this).attr("placeholder"));
                        $(this).focus(function(){
                            if($(this).val()==$(this).attr("placeholder")) $(this).val("");
                        });
                        $(this).blur(function(){
                            if($(this).val()=="") $(this).val($(this).attr("placeholder"));
                        });
                    }
            });
            //对password框的特殊处理1.创建一个text框 2获取焦点和失去焦点的时候切换
            var pwdField    = $("input[type=password]");
            var pwdVal      = pwdField.attr('placeholder');
            pwdField.after('<input id="pwdPlaceholder" type="text" value='+pwdVal+' autocomplete="off" class="col-md-6"/>');
            var pwdPlaceholder = $('#pwdPlaceholder');
            pwdPlaceholder.show();
            pwdField.hide();

            pwdPlaceholder.focus(function(){
                pwdPlaceholder.hide();
                pwdField.show();
                pwdField.focus();
            });

            pwdField.blur(function(){
                if(pwdField.val() == '') {
                    pwdPlaceholder.show();
                    pwdField.hide();
                }
            });

        }
    });

}