1、方法一

function number_format(str) {
if (/[^0-9.-]/.test(str)) {
return “\u5fc5\u987b\u662f\u6570\u5b57\uff01”;
}
str = str.replace(/^(\d*)/,"1.”);
str = (str + “00”).replace(/(\d*.\d\d)\d*/, “1”);str=str.replace(“.”,“,”);varre=/(\d)(\d3,)/;while(re.test(str))str=str.replace(re,“$1,$

function number_format(num) {
return num && num
.toString()
.replace(/(^|\s)\d+/g, (m) => m.replace(/(?=(?!\b)(\d{3})+$)/g, ‘,’))
}
注：當數為20000的話，結果為：20，000