There are multiple JS libraries that allow export to excel. But what if we want to follow a minimalist approach avoiding extra dependencies.

The simplest approach would be to produce CSV from JSON that can easily be opened in excel.

But before I show the conversion logic, let's understand what CSV is and which encoding we shall use when creating a CSV file.

CSV format

This RFC 4180 Common Format and MIME Type for Comma-Separated Values (CSV) Files specifies definition of the CSV format. Note that this is a memo only as the CSV format is not officially standardized.

Main definitions

1. Each record is located on a separate line, delimited by a line break (CRLF).
2. The last record in the file may or may not have an ending line break.
3. Header should contain the same number of fields throughout the file.
4. Each field may or may not be enclosed in double quotes.
5. Fields containing line breaks (CRLF), double quotes, and commas should be enclosed in double-quotes.
6. If double-quotes are used to enclose fields, then a double-quote appearing inside a field must be escaped by preceding it with another double quote.

Encoding

In my JSON data I have characters æ å ø from ISO Latin-1 (ISO/IEC 8859-1) character set that have to be considered when creating a csv file.

Some excerpts The Unicode® Standard Version 15.0 to consider.

Unicode vs UTF-8/16/32

From The Unicode® Standard Version 15.0:

• Unicode is the universal character encoding standard for written characters and text, containing 149,186 characters from the world’s scripts.
• Unicode characters are represented in one of three encoding forms: a 32-bit form (UTF-32), a 16-bit form (UTF-16), and an 8-bit form (UTF-8).
• The Unicode Consortium fully endorses the use of any of the three Unicode encoding forms as a conformant way of implementing the Unicode Standard. It is important not to fall into the trap of trying to distinguish “UTF-8 versus Unicode,” for example. UTF-8, UTF-16, and UTF-32 are all equally valid and conformant ways of implementing the encoded characters of the Unicode Standard.

Byte Order Mark (BOM)

• The character U+FEFF (UTF-8 EF BB BF) used for the byte order mark is named zero width no-break space.
• The UTF-16 and UTF-32 encoding forms of Unicode plain text are sensitive to the byte ordering that is used when writing data to a file.
• Identification of the byte sequence at the beginning of a data stream can be taken as a near-certain indication that the data stream is using the UTF-8 encoding scheme.

In short, adding zero width no-break space before the CSV string will enforce Excel to apply UTF-8 encoding instead of 1252: Western European (Windows) or some other encoding which Excel will choose in case the U+FEFF character is not provided.

I will show the difference between producing CSV file with zero width no-break space and without it in the next post of this series...