金額 format string

var result = '0,0.' + Array(decimalPlace + 1).join('0')
result = result.replace(/\.\s*$/, "");

decimalPlace 0: "0,0"
decimalPlace 1: "0,0.0"
decimalPlace 2: "0,0.00"

參考：

Repeat Character N Times

Remove Last Comma from a string