docs: function getFactor(v) {
    let factor = 1;
    if (v === Infinity || v === -Infinity) {
      throw new Error('Not support Infinity!');
    }
    if (v < 1) {
      let count = 0;
      while (v < 1) {
        factor = factor / 10;
        v = v * 10;
        count++;
      }
      // 浮点数计算出现问题
      if (factor.toString().length > DECIMAL_LENGTH) {
        factor = parseFloat(factor.toFixed(count));
      }
    } else {
      while (v > 10) {
        factor = factor * 10;
        v = v / 10;
      }
    }
  
    return factor;
  }