Floating point error while reading excel file from js

Question

I am reading an excel file that has decimal, string, and Unicode characters when the user uploads it. I am seeing a floating point error when reading some decimal values(not all). For example, if a number is 0.15 then it is read as 0.150000000002. I need to compare data from the same excel file which is read and stored in DB to the data read from excel to find the difference in both. I am using xlxs-js and also tried using exceljs but was not able to resolve the issue.

   reader.onload = (e: any) => {
     /* read workbook */
     const bstr: any = e.target.result;
     const wb: XLSX.WorkBook = XLSX.read(bstr, {type: 'buffer'});

     /* grab first sheet */
     const wsname: string = wb.SheetNames[1];
     const ws: XLSX.WorkSheet = wb.Sheets[wsname];

     /* save data */
     this.data = (XLSX.utils.sheet_to_json(ws, {header: 1}));
     console.log(this.data)
   };
   reader.readAsArrayBuffer(target.files[0]);```

Flashtube · Accepted Answer · 2021-08-30 11:24:21Z

1

Javascript has some issues with floating point numbers.

For example:

0.1 + 0.2
=> 0.30000000000000004

If your floating point numbers all have the same amount of decimal places, I would recommend just removing these floating point digits.

parseFloat((0.1 + 0.2).toFixed(2))
=> 0.3

This is not very elegant and does not work if you have different amounts of decimal places.

I would need more information about how your this.data object looks to give you a code snippet to refactor your this.data object / array.

answered Aug 30, 2021 at 11:24

Flashtube

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