code: function format(value, unitInfo) {
    const unit = unitInfo.unit;
    const precision = unitInfo.precision || 0;
    let v = 0;
    switch (unit) {
      case 'GB':
        v = value / GB;
        break;
      case 'MB':
        v = value / MB;
        break;
      default:
        v = value;
        break;
    }
    v = parseFloat(Number(v).toFixed(precision));
    return v;
  }
docs: Format the bytes by unit
  @param {Number} value Bytes count
  @param {Object} unitInfo {unit: String, precision: Number}
  unit: 'GB', 'MB' or 'B'
  precision: the precision of size, default is 0
  @returns {Number}