# ya-csv

Event based CSV parser and writer for Node.js suitable for processing large CSV streams.

  * Designed for high performance and ease of use.
  * RFC 4180 compliance with optional extensions.
  * Zero dependencies.

## Example
```js
// A simple echo program:
var csv = require('ya-csv');

var reader = csv.createCsvStreamReader(process.openStdin());
var writer = csv.createCsvStreamWriter(process.stdout);

reader.addListener('data', function(data) {
    writer.writeRecord(data);
});

reader.addListener('error', function(e) {
    console.error('Oops!');
});
```

## Installation
```bash
npm install ya-csv
```

Current version requires at least Node.js v0.2.3 and it's tested with Node.js v0.4.12, 0.6.11, 0.7.5 and v0.10.24. Hope it works with the other versions in between too.

## Features

 - event based, suitable for processing big CSV streams
 - configurable separator, quote and escape characters (comma, double-quote and double-quote by default)
 - ignores lines starting with configurable comment character (off by default)
 - supports memory-only streaming

## More examples

Echo first column of the `data.csv` file:
```js
// equivalent of csv.createCsvFileReader('data.csv') 
var reader = csv.createCsvFileReader('data.csv', {
    'separator': ',',
    'quote': '"',
    'escape': '"',       
    'comment': '',
});
var writer = new csv.CsvWriter(process.stdout);
reader.addListener('data', function(data) {
    writer.writeRecord([ data[0] ]);
});
```

Return data in objects rather than arrays: either by grabbing the column names from the header row (first row is not passed to the `data` listener):
```js
var reader = csv.createCsvFileReader('data.csv', { columnsFromHeader: true });
reader.addListener('data', function(data) {
    // supposing there are so named columns in the source file
    sys.puts(data.col1 + " ... " + data.col2);
});
```

... or by providing column names from the client code (first row is passed to the `data` listener in this case):
```js
var reader = csv.createCsvFileReader('data.csv');
reader.setColumnNames([ 'col1', 'col2' ]);
reader.addListener('data', function(data) {
    sys.puts(data.col1 + " ... " + data.col2);
});
```

Note `reader.setColumnNames()` resets the column names so next invocation of the `data` listener will again receive the data in an array rather than an object.

Convert the `/etc/passwd` file to comma separated format, drop commented lines and dump the results to the standard output:
```js
var reader = csv.createCsvFileReader('/etc/passwd', {
    'separator': ':',
    'quote': '"',
    'escape': '"',
    'comment': '#',
});
var writer = new csv.CsvWriter(process.stdout);
reader.addListener('data', function(data) {
    writer.writeRecord(data);
});
```

Parsing an upload as the data comes in, using node-formidable:
```js
upload_form.onPart = function(part) {
    if (!part.filename) { upload_form.handlePart(part); return }

    var reader = csv.createCsvFileReader({'comment': '#'});
    reader.addListener('data', function(data) {
        saveRecord(data);
    });

    part.on('data', function(buffer) {
        // Pipe incoming data into the reader.
        reader.parse(buffer);
    });
    part.on('end', function() {
        reader.end()
    })
}
```

## CsvReader Options

Note: the defaults are based on the values from RFC 4180 -
https://tools.ietf.org/html/rfc4180

  * `separator` - field separator (delimiter), default: ',' (comma)
  * `quote` - the character used to enclose fields with white space
    characters, escaping etc., default: '"' (double quote)
  * `escape` - character used to escape the `quote` inside a
    field, default: '"' (double quote). If you are changing `quotechar`
    you may want to change the `escape` to the same value
  * `comment` - parser will ignore this character and all following
    characters on the same line
    the line, default: none
  * `columnNames` - an array of column names, if used, the rows sent to
    the `data` listener are represented as hashes instead of arrays,
    default: none
  * `columnsFromHeader` - boolean value indicating whether the first row
    should be interpreted as a list of header names. If used, the rows
    sent to the `data` listener are represented as hashes instead of arrays,
    default: `false`
  * `nestedQuotes` - boolean value indicating whether the parser should
    try to process a file with unescaped quote characters inside fields,
    default: `false`
  * `flags` - a string with flags to be passed through to
    createRead/WriteStream (only supported via `createCsvFileReader`
    and `createCsvFileWriter` methods), default: none

## CSvWriter Options

  * `separator` - field separator (delimiter), default: ',' (comma)
  * `quote` - the character used to enclose fields with white space
    characters, escaping etc., default: '"' (double quote)
  * `escape` - character used to escape the `quote` inside a
    field, default: '"' (double quote). If you are changing `quotechar`
    you may want to change the `escape` to the same value
  * `escapeFormulas` - boolean value indicating whether the parser should
    escape '=', '+' and '-' with an apostrophe to prevent some programs
    from treating the content as an executable formula, default: `false`