example csv

Comma-Separated Values

This example shows a simple parser for comma-separated values. The input text consists of zero or more lines, and each line contains a series of cells (values) separated by commas. The result of the CSV parser is an array of arrays (matrix) containing the cell values as strings.

For simplicity, we assume the values themselves can contain neither commas nor end-of-line characters. Also, the parser only handles Unix-style line breaks ('\n'). Generalizing the parser to handle quoting and/or escapes, or alternative end-of-line markers, is left as an exercise.

First, import the Comparse library.

P = require('../lib/comparse')

This is the parser for a single cell (zero or more characters except comma or '\n'):

cell = P.noneOf(',\n').concat()

A line contains one or more cells separated by commas.

line = cell.sepBy P.char ','

And, finally, CSV text consists of zero or more lines separated by end-of-line characters. The last line may or may not be followed by the end-of-line character.

csv = line.sepEndBy P.char '\n'

Now, we can test the parser:

try
  console.log csv.parse 'foo,bar\nbaz,mek,42'
catch e
  console.log e.name, 'at offset', e.offset

The result should be [ [ 'foo', 'bar' ], [ 'baz', 'mek', '42' ] ].