js小数失真问题---乘以100或除以100之后保留两位小数

方法一： 

parseFloat((num*100).toFixed(2))

方法二：

    // 除以100保留两位小数点
    function divideByHundred(str) {
      let floatVal = parseFloat(str);
      if (isNaN(floatVal )) {
        return 0;
      }
      floatVal = Math.round(str * 100) / 10000;
      let strVal = floatVal .toString();
      let searchVal = strVal.indexOf('.');
      if (searchVal < 0) {
        searchVal = strVal.length;
        strVal += '.';
      }
      while (strVal.length <= searchVal + 2) {
        strVal += '0';
      }
      return parseFloat(strVal);
    },
    // 乘以100保留两位小数点
    function multipliedByHundred(str) {
      let floatVal = parseFloat(str);
      if (isNaN(floatVal)) {
        return 0;
      }
      floatVal = Math.round(str * 10000) / 100;
      let strVal = floatVal.toString();
      let searchVal = strVal.indexOf('.');
      if (searchVal < 0) {
        searchVal = strVal.length;
        strVal += '.';
      }
      while (strVal.length <= searchVal + 2) {
        strVal += '0';
      }
      return parseFloat(strVal);
    }

用法：multipliedByHundred（0.2120）===>  21.2