code: function format(number, decimals, thousandsSep, decPoint) {
      number = (number + '').replace(/[^0-9+-Ee.]/g, '')
  
      var n = !isFinite(+number) ? 0 : +number,
          prec = !isFinite(+decimals) ? 0 : Math.abs(decimals),
          sep = typeof thousandsSep !== 'string' ? ',' : thousandsSep,
          dec = typeof decPoint !== 'string' ? '.' : decPoint,
          s = ''
  
      s = (prec ? toFixedFix(n, prec) : '' + Math.round(n)).split('.')
      var re = /(-?\d+)(\d{3})/
      while (re.test(s[0])) {
          s[0] = s[0].replace(re, "$1" + sep + "$2")
      }
  
      if ((s[1] || '').length < prec) {
          s[1] = s[1] || ''
          s[1] += new Array(prec - s[1].length + 1).join('0')
      }
      return s.join(dec)
  }
docs: 数字格式化
  @param {*值} number
  @param {*小数位数} decimals
  @param {*千分符} thousandsSep
  @param {*小数点字符} decPoint