datagrid 当前页面统计合计等在Footer页脚。

 如下是效果图：三行的平均值，合计等计算

$.extend($.fn.datagrid.methods, {           //extend 用来新增datagrid 的方法，名字为statistics
    statistics: function (jq) {
     debugger;
        var opt=$(jq).datagrid("options").columns; //获得所有列的信息，如下图所示：

        var rows = $(jq).datagrid("getRows");   //获得行信息，如下图所示：
         
        var footer = new Array();
        footer["sum"] = "";
        footer["avg"] = "";
        footer["max"] = "";
        footer["min"] = "";

//执行完上述语句之后如下图所示：

         
        for(var i=1; i<opt[0].length; i++){
         sum(opt[0][i].field);
          console.log(opt[0][i].sum);
            if(sum(opt[0][i].field)){
                footer["sum"] = footer["sum"] + sum(opt[0][i].field)+ ",";
                console.log(sum(opt[0][i].field));
            }
            if(avg(opt[0][i].field)){
                footer["avg"] = footer["avg"] + avg(opt[0][i].field)+ ",";
            }
            if(max(opt[0][i].field)){
                footer["max"] = footer["max"] + max(opt[0][i].field)+ ",";
            }
            if(min(opt[0][i].field)){
                footer["min"] = footer["min"] + min(opt[0][i].field)+ ",";

//执行完上述语句，结果如下图：

            }
        }
 
        var footerObj = new Array();
        
        if(footer["sum"] != ""){
            var tmp = "{" + footer["sum"].substring(0,footer["sum"].length - 1) + "}";

            var obj = eval("(" + tmp + ")");

 

            if(obj[opt[0][0].field] == undefined){//opt[0][0].field值时itemid，之前计算时，没有算第一列，所以这里obj里取itemid是undefined
                footer["sum"] += """ + opt[0][0].field + "":"<b>当页合计:</b>"";//计算合计的一行里添加之前未计算的第一列为“当页合计”的标签
                obj = eval("({" + footer["sum"] + "})");
            }else{
                obj[opt[0][0].field] = "<b>当页合计:</b>" + obj[opt[0][0].field];
            }
            footerObj.push(obj);//最后为datagrid的reloadFooter函数拼凑一个json

        }
        
        if(footer["avg"] != ""){
            var tmp = "{" + footer["avg"].substring(0,footer["avg"].length - 1) + "}";
            var obj = eval("(" + tmp + ")");
            if(obj[opt[0][0].field] == undefined){
                footer["avg"] += """ + opt[0][0].field + "":"<b>当页均值:</b>"";
                obj = eval("({" + footer["avg"] + "})");
            }else{
                obj[opt[0][0].field] = "<b>当页均值:</b>" + obj[opt[0][0].field];
            }
            footerObj.push(obj);
        }
        
        if(footer["max"] != ""){
            var tmp = "{" + footer["max"].substring(0,footer["max"].length - 1) + "}";
            var obj = eval("(" + tmp + ")");
            
            if(obj[opt[0][0].field] == undefined){
                footer["max"] += """ + opt[0][0].field + "":"<b>当页最大值:</b>"";
                obj = eval("({" + footer["max"] + "})");
            }else{
                obj[opt[0][0].field] = "<b>当页最大值:</b>" + obj[opt[0][0].field];
            }
            footerObj.push(obj);
        }
        
        if(footer["min"] != ""){
            var tmp = "{" + footer["min"].substring(0,footer["min"].length - 1) + "}";
            var obj = eval("(" + tmp + ")");
            
            if(obj[opt[0][0].field] == undefined){
                footer["min"] += """ + opt[0][0].field + "":"<b>当页最小值:</b>"";
                obj = eval("({" + footer["min"] + "})");
            }else{
                obj[opt[0][0].field] = "<b>当页最小值:</b>" + obj[opt[0][0].field];
            }
            footerObj.push(obj);

        }
        
        
        
        if(footerObj.length > 0){
            $(jq).datagrid("reloadFooter",footerObj);

//如下代码是reloadFooter的easyui的源码

/*

reloadFooter:function(jq,_5d1){
return jq.each(function(){
var opts=$.data(this,"datagrid").options;
var dc=$.data(this,"datagrid").dc;
if(_5d1){
$.data(this,"datagrid").footer=_5d1;//_51d就是$(jq).datagrid("reloadFooter",footerObj); 的footerObj
}
if(opts.showFooter){//当showFooter为true时，进行展示渲染
opts.view.renderFooter.call(opts.view,this,dc.footer2,false);
opts.view.renderFooter.call(opts.view,this,dc.footer1,true);
if(opts.view.onAfterRender){
opts.view.onAfterRender.call(opts.view,this);
}
$(this).datagrid("fixRowHeight");
}
});
}

*/
        }
        
        
        function sum(filed){
            var sumNum = 0;
            for(var i=0;i<rows.length;i++){
             if(isNaN(Number(rows[i][filed])))
              continue;
                sumNum += Number(rows[i][filed]);
            }
            return """ + filed + "":"" + sumNum.toFixed(2) +""";
        };
        
        function avg(filed){
            var sumNum = 0;
            for(var i=0;i<rows.length;i++){
             if(isNaN(Number(rows[i][filed])))
              continue;
                sumNum += Number(rows[i][filed]);
            }
            return """ + filed + "":""+ (sumNum/rows.length).toFixed(2) +""";
        }
 
        function max(filed){
            var max = 0;
            for(var i=0;i<rows.length;i++){
                if(i==0){
                 if(isNaN(Number(rows[i][filed])))
                  continue;
                    max = Number(rows[i][filed]);
                }else{
                 if(isNaN(Number(rows[i][filed])))
                  continue;
                    max = Math.max(max,Number(rows[i][filed]));
                }
            }
            return """ + filed + "":""+ max +""";
        }
        
        function min(filed){
            var min = 0;
            for(var i=0;i<rows.length;i++){
                if(i==0){
                 if(isNaN(Number(rows[i][filed])))
                  continue;
                    min = Number(rows[i][filed]);
                }else{
                 if(isNaN(Number(rows[i][filed])))
                  continue;
                    min = Math.min(min,Number(rows[i][filed]));
                }
            }
            return """ + filed + "":""+ min +""";
        }
    }
});