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;
}