做后台管理界面時，EasyUI 的 DataGrid 經常會被用到，有時候一些總的統計數據不合適放在數據表格里，需要單獨顯示，這時候就可以放在Footer中顯示而不必另外布局。
該怎么給 DataGrid 添加 Footer，Document 里面說的不是很詳細，Demo 里面有這個例子，看 datagrid_data2.json 數據格式就明白了。
{"total":28,"rows":[
{"productid":"FI-SW-01","unitcost":10.00,"status":"P","listprice":36.50,"attr1":"Large","itemid":"EST-1"},
{"productid":"K9-DL-01","unitcost":12.00,"status":"P","listprice":18.50,"attr1":"Spotted Adult Female","itemid":"EST-10"},
{"productid":"RP-SN-01","unitcost":12.00,"status":"P","listprice":28.50,"attr1":"Venomless","itemid":"EST-11"},
{"productid":"RP-SN-01","unitcost":12.00,"status":"P","listprice":26.50,"attr1":"Rattleless","itemid":"EST-12"},
{"productid":"RP-LI-02","unitcost":12.00,"status":"P","listprice":35.50,"attr1":"Green Adult","itemid":"EST-13"},
{"productid":"FL-DSH-01","unitcost":12.00,"status":"P","listprice":158.50,"attr1":"Tailless","itemid":"EST-14"},
{"productid":"FL-DSH-01","unitcost":12.00,"status":"P","listprice":83.50,"attr1":"With tail","itemid":"EST-15"},
{"productid":"FL-DLH-02","unitcost":12.00,"status":"P","listprice":63.50,"attr1":"Adult Female","itemid":"EST-16"},
{"productid":"FL-DLH-02","unitcost":12.00,"status":"P","listprice":89.50,"attr1":"Adult Male","itemid":"EST-17"},
{"productid":"AV-CB-01","unitcost":92.00,"status":"P","listprice":63.50,"attr1":"Adult Male","itemid":"EST-18"}
],"footer":[
{"unitcost":19.80,"listprice":60.40,"productid":"Average:"},
{"unitcost":198.00,"listprice":604.00,"productid":"Total:"}
]}
還有一種更直觀的方法是，在
data-options中用“footer”屬性指定一個ID選擇器，但是這個屬性在Document中沒有說明，至少我沒找到。
<table class="easyui-datagrid" data-options="toolbar:'#tb',footer:'#ft'">
這個在官方例子 DataGrid Complex Toolbar 中可以看到
