function formatNumber(val){ if (val === undefined){ return '暂无数据' } else if (isNaN(+val)){ return val } else if (!val){ return 0 } let newVal = val.toString() let arr = newVal.split('.') let inpart = arr[0].replace(/(\d)(?=(?:\d{3})+$)/g,'$1,') if (arr[1]){ return inpart + '.' + arr[1] }else { return inpart }}console.log(formatNumber(12345678));