docs.sheetjs.com/docz/docs/07-csf/07-features/06-nf.md

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# Number Formats

<details>
  <summary><b>File Format Support</b> (click to show)</summary>

Legacy formats like CSV mix "content" and "presentation". There is no true
concept of a "number format" distinct from the number itself. For specific
formats, the library will guess the number format.

| Formats           | Basic | Storage Representation |
|:------------------|:-----:|:-----------------------|
| XLSX / XLSM       |   ✔   | Number Format Code     |
| XLSB              |   ✔   | Number Format Code     |
| XLS               |   ✔   | Number Format Code     |
| XLML              |   ✔   | Number Format Code     |
| SYLK              |   R   | Number Format Code     |
| ODS / FODS / UOS  |   ✔   | XML                    |
| NUMBERS           |       | Binary encoding        |
| WK\*              |       | Binary encoding        |
| WQ\* / WB\* / QPW |       | Binary encoding        |
| DBF               |       | Implied by field types |
| HTML              |   *   | Special override       |
| CSV               |   *   | N/A                    |
| PRN               |   *   | N/A                    |
| DIF               |   *   | N/A                    |
| RTF               |   *   | N/A                    |

Asterisks (*) mark formats that mix content and presentation. Writers will use
formatted values if cell objects include formatted text or number formats.
Parsers may guess number formats for special values.

The letter R (R) marks features parsed but not written in the format.

</details>

This example generates a worksheet with common number formats. `sheet_to_html`
uses the number formats in generating the HTML table. The "Export" button
generates workbooks with number formatting.

```jsx live
function SheetJSSimpleNF(props) {
  const [ws, setWS] = React.useState();
  const fmt = React.useRef(null);

  /* when the page is loaded, create worksheet and show table */
  React.useEffect(() => {
    /* Create worksheet from simple data */
    const ws = XLSX.utils.aoa_to_sheet([
      ["General",   54337      ],
      ["Currency",      3.5    ],
      ["Thousands",  7262      ],
      ["Percent",       0.0219 ],
    ]);

    /* assign number formats */
    ws["B2"].z = '"$"#,##0.00_);\\("$"#,##0.00\\)';
    ws["B3"].z = '#,##0';
    ws["B4"].z = "0.00%";

    setWS(ws);
  }, []);

  const xport = (fmt) => {
    /* Export to file (start a download) */
    const wb = XLSX.utils.book_new();
    XLSX.utils.book_append_sheet(wb, ws, "Formats");
    XLSX.writeFile(wb, `SheetJSSimpleNF.${fmt}`);
  };

  const fmts = ["xlsx", "xls", "csv", "xlsb", "html", "ods"];
  return ( <>
    <select ref={fmt}>{fmts.map(fmt => (<option value={fmt}>{fmt}</option>))}</select>
    <button onClick={()=>xport(fmt.current.value)}><b>Export!</b></button>
    <div dangerouslySetInnerHTML={{__html: ws && XLSX.utils.sheet_to_html(ws) || "" }}/>
  </> );
}
```

## Values and Formatting

Typically spreadsheets will include formatted text such as currencies (`$3.50`)
or large numbers with thousands separators (`7,262`) or percentages (`2.19%`).

To simplify editing, the applications will store the underlying values and the
number formats separately. For example, `$3.50` will be represented as the value
`3.5` with a number format that mandates a `$` sigil and 2 decimal places.

CSV and other formats only support the formatted text. Applications reading CSV
files are expected to interpret the values as numbers or dates.

### Dates and Times

Many spreadsheet formats store dates and times using a number that represents
the number of seconds or days after some epoch. Dates are covered in more detail
[in the dedicated section](/docs/csf/features/dates).

## SheetJS Representation

Number formats and values are attached to cells. The following keys are used:

| Key | Description                                                            |
| --- | ---------------------------------------------------------------------- |
| `v` | raw value (number, string, Date object, boolean)                       |
| `z` | number format string associated with the cell (if requested)           |
| `w` | formatted text (if applicable)                                         |

The `cell.w` formatted text for each cell is produced from `cell.v` and `cell.z`
format.  If the format is not specified, the Excel `General` format is used.

By default, parsers do not attach number formats to cells.  The `cellNF` option
instructs `XLSX.read` or `XLSX.readFile` to save the formats.

### Number Format Strings

The `z` format string follows the Excel persistence rules as described in
ECMA-376 18.8.31 (Number Formats). For more info, see the Excel documentation
article `Create or delete a custom number format`

The rules are slightly different from how Excel displays custom number formats.
In particular, literal characters must be wrapped in double quotes or preceded
by a backslash.

The following example prints number formats from a user-specified file:

```jsx live
function SheetJSExtractNF(props) {
  const [rows, setRows] = React.useState([])

  return ( <>
    <input type="file" onChange={async(e) => {
      /* parse workbook with cellNF: true */
      const wb = XLSX.read(await e.target.files[0].arrayBuffer(), {cellNF: true});

      /* look at each cell in each worksheet */
      const formats = {};
      wb.SheetNames.forEach(n => {
        var ws = wb.Sheets[n]; if(!ws || !ws["!ref"]) return;
        var ref = XLSX.utils.decode_range(ws["!ref"]);
        for(var R = 0; R <= ref.e.r; ++R) for(var C = 0; C <= ref.e.c; ++C) {
          var addr = XLSX.utils.encode_cell({r:R,c:C});
          if(!ws[addr] || !ws[addr].z || formats[ws[addr].z]) continue;
          /* when a new format is found, save the address */
          formats[ws[addr].z] = `'${n}'!${addr}`;
          setRows(Object.entries(formats));
        }
      });
    }}/>
    <table><tr><th>Format</th><th>JSON</th><th>Example Cell</th></tr>
    {rows.map((r,R) => ( <tr key={R}>
      <td><code>{r[0]}</code></td>
      <td><code>{JSON.stringify(r[0])}</code></td>
      <td>{r[1]}</td>
    </tr> ))}
    </table>
  </> );
}
```

## Miscellany

The default formats are listed in ECMA-376 18.8.30:

<details>
  <summary><b>Default Number Formats</b> (click to show)</summary>

| ID | Format                     |
|---:|:---------------------------|
|  0 | `General`                  |
|  1 | `0`                        |
|  2 | `0.00`                     |
|  3 | `#,##0`                    |
|  4 | `#,##0.00`                 |
|  9 | `0%`                       |
| 10 | `0.00%`                    |
| 11 | `0.00E+00`                 |
| 12 | `# ?/?`                    |
| 13 | `# ??/??`                  |
| 14 | `m/d/yy` (see below)       |
| 15 | `d-mmm-yy`                 |
| 16 | `d-mmm`                    |
| 17 | `mmm-yy`                   |
| 18 | `h:mm AM/PM`               |
| 19 | `h:mm:ss AM/PM`            |
| 20 | `h:mm`                     |
| 21 | `h:mm:ss`                  |
| 22 | `m/d/yy h:mm`              |
| 37 | `#,##0 ;(#,##0)`           |
| 38 | `#,##0 ;[Red](#,##0)`      |
| 39 | `#,##0.00;(#,##0.00)`      |
| 40 | `#,##0.00;[Red](#,##0.00)` |
| 45 | `mm:ss`                    |
| 46 | `[h]:mm:ss`                |
| 47 | `mmss.0`                   |
| 48 | `##0.0E+0`                 |
| 49 | `@`                        |

</details>

Format 14 (`m/d/yy`) is localized by Excel: even though the file specifies that
number format, it will be drawn differently based on system settings.  It makes
sense when the producer and consumer of files are in the same locale, but that
is not always the case over the Internet.  To get around this ambiguity, parse
functions accept the `dateNF` option to override the interpretation of that
specific format string.

### Excel Format Categories

Excel officially recognizes a small number of formats as "Currency" and another
set of formats as "Accounting".  The exact formats in `en-US` are listed below:

#### Currency

| JS String                                | Decimal Places | Negative Color |
|:-----------------------------------------|:---------------|:---------------|
| `'"$"#,##0_);\\("$"#,##0\\)'`            | 0              | Black          |
| `'"$"#,##0_);[Red]\\("$"#,##0\\)'`       | 0              | Red            |
| `'"$"#,##0.00_);\\("$"#,##0.00\\)'`      | 2              | Black          |
| `'"$"#,##0.00_);[Red]\\("$"#,##0.00\\)'` | 2              | Red            |

#### Accounting

| JS String                                                        | Decimal | Sigil |
|:-----------------------------------------------------------------|:--------|:------|
| `'_(* #,##0_);_(* \\(#,##0\\);_(* "-"_);_(@_)'`                  | 0       |       |
| `'_("$"* #,##0_);_("$"* \\(#,##0\\);_("$"* "-"_);_(@_)'`         | 0       | `$`   |
| `'_(* #,##0.00_);_(* \\(#,##0.00\\);_(* "-"??_);_(@_)'`          | 2       |       |
| `'_("$"* #,##0.00_);_("$"* \\(#,##0.00\\);_("$"* "-"??_);_(@_)'` | 2       | `$`   |

For other locales, the formats can be discovered by creating a file with the
desired format and testing with [the Number Format Strings demo](#number-format-strings)

### HTML Override

[**This feature is discussed in the HTML utilities section**](/docs/api/utilities/html#value-override)