## Parsing Options

The exported `read` and `readFile` functions accept an options argument:

| Option Name | Default | Description                                          |
| :---------- | ------: | :--------------------------------------------------- |
| type        |         | Input data encoding (see Input Type below)           |
| cellFormula | true    | Save formulae to the .f field                        |
| cellHTML    | true    | Parse rich text and save HTML to the .h field        |
| cellNF      | false   | Save number format string to the .z field            |
| cellStyles  | false   | Save style/theme info to the .s field                |
| cellDates   | false   | Store dates as type `d` (default is `n`)             |
| sheetStubs  | false   | Create cell objects of type `z` for stub cells       |
| sheetRows   | 0       | If >0, read the first `sheetRows` rows **            |
| bookDeps    | false   | If true, parse calculation chains                    |
| bookFiles   | false   | If true, add raw files to book object **             |
| bookProps   | false   | If true, only parse enough to get book metadata **   |
| bookSheets  | false   | If true, only parse enough to get the sheet names    |
| bookVBA     | false   | If true, expose vbaProject.bin to `vbaraw` field **  |
| password    | ""      | If defined and file is encrypted, use password **    |
| WTF         | false   | If true, throw errors on unexpected file features ** |

- Even if `cellNF` is false, formatted text will be generated and saved to `.w`
- In some cases, sheets may be parsed even if `bookSheets` is false.
- `bookSheets` and `bookProps` combine to give both sets of information
- `Deps` will be an empty object if `bookDeps` is falsy
- `bookFiles` behavior depends on file type:
    * `keys` array (paths in the ZIP) for ZIP-based formats
    * `files` hash (mapping paths to objects representing the files) for ZIP
    * `cfb` object for formats using CFB containers
- `sheetRows-1` rows will be generated when looking at the JSON object output
  (since the header row is counted as a row when parsing the data)
- `bookVBA` merely exposes the raw vba object.  It does not parse the data.
- Currently only XOR encryption is supported.  Unsupported error will be thrown
  for files employing other encryption methods.
- WTF is mainly for development.  By default, the parser will suppress read
  errors on single worksheets, allowing you to read from the worksheets that do
  parse properly. Setting `WTF:1` forces those errors to be thrown.

The defaults are enumerated in bits/84\_defaults.js

### Input Type

Strings can be interpreted in multiple ways.  The `type` parameter for `read`
tells the library how to parse the data argument:

| `type`     | expected input                                                  |
|------------|-----------------------------------------------------------------|
| `"base64"` | string: base64 encoding of the file                             |
| `"binary"` | string:  binary string (`n`-th byte is `data.charCodeAt(n)`)    |
| `"buffer"` | nodejs Buffer                                                   |
| `"array"`  | array: array of 8-bit unsigned int (`n`-th byte is `data[n]`)   |
| `"file"`   | string: filename that will be read and processed (nodejs only)  |

### Guessing File Type

Excel and other spreadsheet tools read the first few bytes and apply other
heuristics to determine a file type.  This enables file type punning: renaming
files with the `.xls` extension will tell your computer to use Excel to open the
file but Excel will know how to handle it.  This library applies similar logic:

| Byte 0 | Raw File Type | Spreadsheet Types                                   |
|:-------|:--------------|:----------------------------------------------------|
| `0xD0` | CFB Container | BIFF 5/8 or password-protected XLSX/XLSB            |
| `0x09` | BIFF Stream   | BIFF 2/3/4/5                                        |
| `0x3C` | XML/HTML      | SpreadsheetML / Flat ODS / UOS1 / HTML / plaintext  |
| `0x50` | ZIP Archive   | XLSB or XLSX/M or ODS or UOS2 or plaintext          |
| `0x49` | Plain Text    | SYLK or plaintext                                   |
| `0x54` | Plain Text    | DIF or plaintext                                    |
| `0xFE` | UTF8 Text     | SpreadsheetML or Flat ODS or UOS1 or plaintext      |

DBF files are detected based on the first byte as well as the third and fourth
bytes (corresponding to month and day of the file date)