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[tests-url]: http://travis-ci.org/mafintosh/csv-parser
[cover]: https://codecov.io/gh/mafintosh/csv-parser/branch/master/graph/badge.svg
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[size-url]: https://packagephobia.now.sh/result?p=csv-parser
# csv-parser
[![tests][tests]][tests-url]
[![cover][cover]][cover-url]
[![size][size]][size-url]
Streaming CSV parser that aims for maximum speed as well as compatibility with
the [csv-spectrum](https://npmjs.org/csv-spectrum) CSV acid test suite.
`csv-parser` can convert CSV into JSON at at rate of around 90,000 rows per
second. Performance varies with the data used; try `bin/bench.js <your file>`
to benchmark your data.
`csv-parser` can be used in the browser with [browserify](http://browserify.org/).
[neat-csv](https://github.com/sindresorhus/neat-csv) can be used if a `Promise`
based interface to `csv-parser` is needed.
_Note: This module requires Node v8.16.0 or higher._
## Benchmarks
⚡️ `csv-parser` is greased-lightning fast
```console
→ npm run bench
Filename Rows Parsed Duration
backtick.csv 2 3.5ms
bad-data.csv 3 0.55ms
basic.csv 1 0.26ms
comma-in-quote.csv 1 0.29ms
comment.csv 2 0.40ms
empty-columns.csv 1 0.40ms
escape-quotes.csv 3 0.38ms
geojson.csv 3 0.46ms
large-dataset.csv 7268 73ms
newlines.csv 3 0.35ms
no-headers.csv 3 0.26ms
option-comment.csv 2 0.24ms
option-escape.csv 3 0.25ms
option-maxRowBytes.csv 4577 39ms
option-newline.csv 0 0.47ms
option-quote-escape.csv 3 0.33ms
option-quote-many.csv 3 0.38ms
option-quote.csv 2 0.22ms
quotes+newlines.csv 3 0.20ms
strict.csv 3 0.22ms
latin.csv 2 0.38ms
mac-newlines.csv 2 0.28ms
utf16-big.csv 2 0.33ms
utf16.csv 2 0.26ms
utf8.csv 2 0.24ms
```
## Install
Using npm:
```console
$ npm install csv-parser
```
Using yarn:
```console
$ yarn add csv-parser
```
## Usage
To use the module, create a readable stream to a desired CSV file, instantiate
`csv`, and pipe the stream to `csv`.
Suppose you have a CSV file `data.csv` which contains the data:
```
NAME,AGE
Daffy Duck,24
Bugs Bunny,22
```
It could then be parsed, and results shown like so:
``` js
const csv = require('csv-parser')
const fs = require('fs')
const results = [];
fs.createReadStream('data.csv')
.pipe(csv())
.on('data', (data) => results.push(data))
.on('end', () => {
console.log(results);
// [
// { NAME: 'Daffy Duck', AGE: '24' },
// { NAME: 'Bugs Bunny', AGE: '22' }
// ]
});
```
To specify options for `csv`, pass an object argument to the function. For
example:
```js
csv({ separator: '\t' });
```
## API
### csv([options | headers])
Returns: `Array[Object]`
#### options
Type: `Object`
As an alternative to passing an `options` object, you may pass an `Array[String]`
which specifies the headers to use. For example:
```js
csv(['Name', 'Age']);
```
If you need to specify options _and_ headers, please use the the object notation
with the `headers` property as shown below.
#### escape
Type: `String`<br>
Default: `"`
A single-character string used to specify the character used to escape strings
in a CSV row.
#### headers
Type: `Array[String] | Boolean`
Specifies the headers to use. Headers define the property key for each value in
a CSV row. If no `headers` option is provided, `csv-parser` will use the first
line in a CSV file as the header specification.
If `false`, specifies that the first row in a data file does _not_ contain
headers, and instructs the parser to use the column index as the key for each column.
Using `headers: false` with the same `data.csv` example from above would yield:
``` js
[
{ '0': 'Daffy Duck', '1': 24 },
{ '0': 'Bugs Bunny', '1': 22 }
]
```
_Note: If using the `headers` for an operation on a file which contains headers on the first line, specify `skipLines: 1` to skip over the row, or the headers row will appear as normal row data. Alternatively, use the `mapHeaders` option to manipulate existing headers in that scenario._
#### mapHeaders
Type: `Function`
A function that can be used to modify the values of each header. Return a `String` to modify the header. Return `null` to remove the header, and it's column, from the results.
```js
csv({
mapHeaders: ({ header, index }) => header.toLowerCase()
})
```
##### Parameters
**header** _String_ The current column header.<br/>
**index** _Number_ The current column index.
#### mapValues
Type: `Function`
A function that can be used to modify the content of each column. The return value will replace the current column content.
```js
csv({
mapValues: ({ header, index, value }) => value.toLowerCase()
})
```
##### Parameters
**header** _String_ The current column header.<br/>
**index** _Number_ The current column index.<br/>
**value** _String_ The current column value (or content).
##### newline
Type: `String`<br>
Default: `\n`
Specifies a single-character string to denote the end of a line in a CSV file.
#### quote
Type: `String`<br>
Default: `"`
Specifies a single-character string to denote a quoted string.
#### raw
Type: `Boolean`<br>
If `true`, instructs the parser not to decode UTF-8 strings.
#### separator
Type: `String`<br>
Default: `,`
Specifies a single-character string to use as the column separator for each row.
#### skipComments
Type: `Boolean | String`<br>
Default: `false`
Instructs the parser to ignore lines which represent comments in a CSV file. Since there is no specification that dictates what a CSV comment looks like, comments should be considered non-standard. The "most common" character used to signify a comment in a CSV file is `"#"`. If this option is set to `true`, lines which begin with `#` will be skipped. If a custom character is needed to denote a commented line, this option may be set to a string which represents the leading character(s) signifying a comment line.
#### skipLines
Type: `Number`<br>
Default: `0`
Specifies the number of lines at the beginning of a data file that the parser should
skip over, prior to parsing headers.
#### maxRowBytes
Type: `Number`<br>
Default: `Number.MAX_SAFE_INTEGER`
Maximum number of bytes per row. An error is thrown if a line exeeds this value. The default value is on 8 peta byte.
#### strict
Type: `Boolean`<br>
Default: `false`
If `true`, instructs the parser that the number of columns in each row must match
the number of `headers` specified or throws an exception.
if `false`: the headers are mapped to the column index
less columns: any missing column in the middle will result in a wrong property mapping!
more columns: the aditional columns will create a "_"+index properties - eg. "_10":"value"
## Events
The following events are emitted during parsing:
### `data`
Emitted for each row of data parsed with the notable exception of the header
row. Please see [Usage](#Usage) for an example.
### `headers`
Emitted after the header row is parsed. The first parameter of the event
callback is an `Array[String]` containing the header names.
```js
fs.createReadStream('data.csv')
.pipe(csv())
.on('headers', (headers) => {
console.log(`First header: ${headers[0]}`)
})
```
### Readable Stream Events
Events available on Node built-in
[Readable Streams](https://nodejs.org/api/stream.html#stream_class_stream_readable)
are also emitted. The `end` event should be used to detect the end of parsing.
## CLI
This module also provides a CLI which will convert CSV to
[newline-delimited](http://ndjson.org/) JSON. The following CLI flags can be
used to control how input is parsed:
```
Usage: csv-parser [filename?] [options]
--escape,-e Set the escape character (defaults to quote value)
--headers,-h Explicitly specify csv headers as a comma separated list
--help Show this help
--output,-o Set output file. Defaults to stdout
--quote,-q Set the quote character ('"' by default)
--remove Remove columns from output by header name
--separator,-s Set the separator character ("," by default)
--skipComments,-c Skip CSV comments that begin with '#'. Set a value to change the comment character.
--skipLines,-l Set the number of lines to skip to before parsing headers
--strict Require column length match headers length
--version,-v Print out the installed version
```
For example; to parse a TSV file:
```
cat data.tsv | csv-parser -s $'\t'
```
## Encoding
Users may encounter issues with the encoding of a CSV file. Transcoding the
source stream can be done neatly with a modules such as:
- [`iconv-lite`](https://www.npmjs.com/package/iconv-lite)
- [`iconv`](https://www.npmjs.com/package/iconv)
Or native [`iconv`](http://man7.org/linux/man-pages/man1/iconv.1.html) if part
of a pipeline.
## Byte Order Marks
Some CSV files may be generated with, or contain a leading [Byte Order Mark](https://en.wikipedia.org/wiki/Byte_order_mark#UTF-8). This may cause issues parsing headers and/or data from your file. From Wikipedia:
>The Unicode Standard permits the BOM in UTF-8, but does not require nor recommend its use. Byte order has no meaning in UTF-8.
To use this module with a file containing a BOM, please use a module like [strip-bom-stream](https://github.com/sindresorhus/strip-bom-stream) in your pipeline:
```js
const fs = require('fs');
const csv = require('csv-parser');
const stripBom = require('strip-bom-stream');
fs.createReadStream('data.csv')
.pipe(stripBom())
.pipe(csv())
...
```
When using the CLI, the BOM can be removed by first running:
```console
$ sed $'s/\xEF\xBB\xBF//g' data.csv
```
## Meta
[CONTRIBUTING](./.github/CONTRIBUTING)
[LICENSE (MIT)](./LICENSE)
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