js 一些小技巧

1,表单中,回车导致下一个表单元素聚焦
Js代码

/***
enter to make next object focus
*/
var pressFocusNext=function(event,next22){
    if(!event ||event==undefined){
        event=window.event;
    }
    if(event.keyCode==13){//Enter
        if(typeof next22 == 'string'){
            next22=com.whuang.hsj.$$one(next22);
        }
        if(next22 && next22!=undefined){
            next22.focus();
        }  

    }
}  

使用场景:
Html代码

<form id="leaveMessageForm" style="margin-bottom: 4px;width: 100%"  >  

                       <ul>
                           <li><label>单位名称</label><input type="text" name="company" placeholder="单位名称"  onkeypress="pressFocusNext(event,'username')" /></li>
                           <li><label>称呼</label><input type="text" name="username" placeholder="您的称呼" onkeypress="pressFocusNext(event,'email')" /></li>
                           <li><label>电话</label><input type="text" name="email" placeholder="您的电话号码"  onkeypress="pressFocusNext(event,'object')" /></li>
                           <li><label>留言标题</label><input type="text" name="object" placeholder="留言标题"  onkeypress="pressFocusNext(event,'content')" /></li>
                           <li class="ly" style="width:100%;" ><label  >留言内容</label>  

                               <textarea  name="content" placeholder="留言内容" ></textarea>  

                           </li>
                           <li class="submit"><input type="button" value="提交" onclick="ajaxSubmitMessage()"  /></li>
                           <li class="reset"><input type="reset"  id="resetId" value="重写"/></li>  

                       </ul>  

                   </form>  

2,对某个表单控件回车触发指定事件
Js代码

/***
 enter to to something identified by responseEvent
 */
var pressEnterTo=function(event,responseEvent){
    if(!event ||event==undefined){
        event=window.event;
    }
    if(event.keyCode==13){//Enter
        responseEvent();
    }
};  

使用场景:
Html代码

<div id="register_user">  

                                        <h2  style="margin-right: -15px;margin-left: -15px" ><span class="fontawesome-user"></span>注册</h2>  

                                        <form action="#" method="POST">  

                                            <fieldset class="submit2">  

                                                <p><label for="username">用户名</label></p>  

                                                <p><input type="text" name="username" placeholder="用户名"
                                                          onkeypress="pressFocusNext(event,$('#register_user input[name=password]'))"
                                                          required></p>  

                                                <p><label for="password">密码</label></p>  

                                                <p><input type="password" name="password" placeholder="密码"
                                                          onkeypress="pressFocusNext(event,$('#repassword'))" required>
                                                </p>  

                                                <p><label for="repassword">确认密码</label></p>  

                                                <p><input type="password" id="repassword" placeholder="确认密码"
                                                          onkeypress="pressFocusNext(event,$('#register_user input[name=email]'))"
                                                          required></p>  

                                                <p><label for="email">电子邮箱</label></p>  

                                                <p><input type="text" name="email" placeholder="电子邮箱"
                                                          onkeypress="pressEnterTo(event,user.register)" required></p>  

                                                <p><input type="button" id="registerBtn" onclick="user.register();"
                                                          value="注册"></p>  

                                            </fieldset>  

                                        </form>  

                                    </div> <!-- end login -->  

对最后一个表单元素回车时触发登录
3,使div居中
Js代码

/***
 * make dialog in center
 */
com.whuang.hsj.centerJQueryPos = function ($div22, isApplyVertical/*是否竖直方向也居中*/, isIncludeScroll/*是否包含滚动条高度*/) {
    var width = $div22.width();
    var height = $div22.height();  

    var left = (getInner().width - width) / 2 + com.whuang.hsj.getScroll().left;
    var param = {'left': left};
    if (arguments.length === 1 || isApplyVertical) {//Vertical direction
        var top = (getInner().height - height) / 2;
        if (isIncludeScroll) {
            top = top + com.whuang.hsj.getScroll().top;
        }
        param['top'] = top;
    }
    $div22.css(param);
};//centerJQueryPos
com.whuang.hsj.centerX = function ($div22) {//只水平方向居中
    com.whuang.hsj.centerJQueryPos($div22, false, false);
};
com.whuang.hsj.centerXY = function ($div22) {//水平方向和竖直方向同时居中
    com.whuang.hsj.centerJQueryPos($div22, true, false);
};
//Cross browser gets the position of scroll
com.whuang.hsj.getScroll=function(){
    return {
        top:document.documentElement.scrollTop || document.body.scrollTop,
left:document.documentElement.scrollLeft || document.body.scrollLeft,
height:document.documentElement.scrollHeight ||document.body.scrollHeight
};
};

使用场景:
Js代码

if (isCenter) {
               jqueryObjParam.$dialogPanel.show('normal', function () {
                   com.whuang.hsj.centerXY(jqueryObjParam.$dialogPanel);
                   jqueryObjParam.$dialogPanel.css("position", 'fixed');//保证固定在可视范围内
               });  

           }  

注意:div的position的值必须是fixed或absolute
4,获取浏览器可视区域的大小,与是否有滚动条无关
Js代码

//Cross browser gets the size of Visual area window,Have nothing to do with scroll bars
var getInner=(function() {
    // alert(typeof window.innerWidth !== 'undefined');
    if (typeof window.innerWidth !== 'undefined') {//Notice:'undefined' is right
        return function(){
            return {
                width : window.innerWidth,
                height : window.innerHeight
            }
        }
    } else {
        return function(){
            return {
                width : document.documentElement.clientWidth,
                height : document.documentElement.clientHeight
            }
        }
    }
})();  

5,日期格式化
Js代码

/***
format date or time
*/
Date.prototype.format =function(format)
{
    var o = {
        "M+" : this.getMonth()+1, //month
        "d+" : this.getDate(), //day
        "h+" : this.getHours(), //hour
        "m+" : this.getMinutes(), //minute
        "s+" : this.getSeconds(), //second
        "q+" : Math.floor((this.getMonth()+3)/3), //quarter
        "S" : this.getMilliseconds() //millisecond
    }
    if(/(y+)/.test(format)) format=format.replace(RegExp.$1,
    (this.getFullYear()+"").substr(4- RegExp.$1.length));
    for(var k in o)if(new RegExp("("+ k +")").test(format))
    format = format.replace(RegExp.$1,
    RegExp.$1.length==1? o[k] :
    ("00"+ o[k]).substr((""+ o[k]).length));
    return format;
}
Date.prototype.format2 = function(fmt)
{ //author: meizz
  var o = {
    "%m" : this.getMonth()+1+'',                 //月份
    "%d" : this.getDate() + '',                  //日
    "%H" : this.getHours()+'',                   //小时
    "%M" : this.getMinutes()+'',                 //分
    "%S" : this.getSeconds()+''                //秒
    //"q+" : Math.floor((this.getMonth()+3)/3), //季度
  };
  // 年份  2015
  if(/(%Y)/.test(fmt))
    fmt=fmt.replace(RegExp.$1, (this.getFullYear()+""));   

  // 两位年份  15
  if(/(%y)/.test(fmt))
    fmt=fmt.replace(RegExp.$1, (this.getFullYear()+"").substr(2));       

  //getTime返回的是以毫秒为单位的，转为秒
  if(/(%s)/.test(fmt))
    //fmt=fmt.replace(RegExp.$1, this.getTime()/1000);
    fmt=fmt.replace(RegExp.$1, (this.getTime()+'').slice(0, 10));   

  for(var k in o)
    if(new RegExp("("+ k +")").test(fmt)){
        fmt = fmt.replace(RegExp.$1, (o[k].length == 2 ? o[k] : '0' + o[k]));
    }
  return fmt;
}
 常用场景:
Js代码
var releaseDate=new Date(Number(obj.releaseTime)*1000).format('yyyy-MM-dd');//把毫秒数转化为日期  

**6,设置和获取html元素的自定义属性**
Js代码
com.whuang.hsj.getCustomAttr=function(htmlNode22,attr)
{
    var hospitalId=htmlNode22[attr];
    if(hospitalId==undefined||hospitalId==null){
        hospitalId=htmlNode22.getAttribute(attr);
    }
    if(hospitalId==undefined||hospitalId==null){
        if(htmlNode22.attributes){
            hospitalId=htmlNode22.attributes[attr].nodeValue;
        }
    }
    return hospitalId;
}
com.whuang.hsj.setCustomAttr=function(htmlNode22,attr22,attrValue)
{
    if(htmlNode22.setAttribute===undefined)
    {
        htmlNode22.attributes[attr22].nodeValue = attrValue;
    }else{
        htmlNode22.setAttribute(attr22,attrValue);  // 设置自定义属性的值
    }
}  

使用场景:
Js代码

var currentPage=com.whuang.hsj.getCustomAttr($ul_list.get(0),"currentPage");
        var isOver=Boolean.parse(com.whuang.hsj.getCustomAttr($ul_list.get(0),"isOver2"));
 com.whuang.hsj.setCustomAttr(newsPanel_ul,"currentPage",data.currentpage);
            com.whuang.hsj.setCustomAttr(newsPanel_ul,"isOver2",data.over);

7,使用jquery时如何判断元素是否为空呢?
错误:if($thisForm==null)
正确:
Js代码

if ($thisForm.length == 0) {
        alert("can not get form ,maybe not pass on form object.");
        return;
    }

Js代码

if(form.length==0){
        alert("没有找到表单");
        return;
    }  

通过length来判断,因为使用jquery获取元素,就算元素不存在也会返回一个对象.
8,如何判断参数是否为空
Js代码

bbs.add_bbsReply = function (self) {
    if (cardid == null) {
        alert("cardid is null");
        return;
    }
    var $thisForm = null;
    if (arguments.length > 0) {//说明传入了参数self
        $thisForm = $(self);
    } else {
        $thisForm = $("#formBBS_reply");
    }
}  

范例:
Js代码

function tabSelect(url, aHref, isNav, showslider) {
    showMask();
    if (isNav) {
        $('#nav li').removeClass("current")/*.removeClass("focus ")*/;
    }  

    if (arguments.length > 3 && showslider) {
        $slider_carousel.show();
        $left_sidebar.show();
    } else {
        $slider_carousel.hide();
        $left_sidebar.hide();
    }
    ajaxHtml(url + "&recordsPerPage=5&random22=" + Math.random(), $exchangeDiv);//page.js
    if (isNav) {
        $(aHref).parent().addClass("current");
    }
    ui_tab_wh(jQuery);
}  

通过arguments.length来判断比通过self==null||self==undefined要好
9,创建对像

var tip = {};

10,使悬浮的div可以拖动
Js代码

com.whuang.hsj.drag = function ($obj, hn) {
    if (arguments.length == 0) {
        return;
    }
    if ($obj == null || $obj == undefined) {
        return;
    }
    if (typeof  $obj == 'string') {//when $obj is a string
        $obj = $($obj);
    }
    var $hn = null;
    if (arguments.length > 1) {
        $hn = $obj.find(hn);//div h1,h2...
    } else {
        $hn = $obj.find("h2");
    }
    $hn.on({
        mousedown: function (e) {
            e.preventDefault();
            var t = $obj.offset(),
                o = e.pageX - t.left,
                i = e.pageY - t.top;
            //$obj.css("position", 'fixed');
            $(document).on("mousemove.drag", function (e) {
                $obj.offset({
                    top: e.pageY - i,
                    left: e.pageX - o
                })
            })
        },
        mouseup: function () {
            $(document).unbind("mousemove.drag");
            $obj.css("position", 'fixed');
        }
    });
};//drag  

使用场景:
Js代码

com.whuang.hsj.drag("#subPagePanel", "h2");//增加拖动对话框的功能
   com.whuang.hsj.drag("#subPageBBS", "h2");