extjs grid的列表示金额的数字显示为千分位

renderer:function(value, meta, record){
 num = value + ""; 
if (num.indexOf(',') > 0) { 
num = num.replace(/,/gi, '') + ""; 
} 
var re = /(-?\d+)(\d{3})/; 
while (re.test(num)) {
 num = num.replace(re, "$1,$2"); 
}
 return num;
}