csvtojson
module is a comprehensive nodejs csv parser to convert csv to json or column arrays. It can be used as node.js library / command line tool / or in browser. Below are some features:
- Strictly follow CSV definition RF4180
- Work with millions of lines of CSV data
- Provide comprehensive parsing parameters
- Provide out of box CSV parsing tool for Command Line
- Blazing fast -- Focus on performance
- Give flexibility to developer with 'pre-defined' helpers
- Allow async / streaming parsing
- Provide a csv parser for both Node.JS and browsers
- Easy to use API
Here is a free online csv to json convert service utilizing latest csvtojson
module.
csvtojson
has released version 2.0.0
.
- To upgrade to v2, please follow upgrading guide
- If you are looking for documentation for
v1
, open this page.
It is still able to use v1 with [email protected]
// v1
const csvtojsonV1=require("csvtojson/v1");
// v2
const csvtojsonV2=require("csvtojson");
const csvtojsonV2=require("csvtojson/v2");
npm i --save csvtojson
/** csv file
a,b,c
1,2,3
4,5,6
*/
const csvFilePath='<path to csv file>'
const csv=require('csvtojson')
csv()
.fromFile(csvFilePath)
.then((jsonObj)=>{
console.log(jsonObj);
/**
* [
* {a:"1", b:"2", c:"3"},
* {a:"4", b:"5". c:"6"}
* ]
*/
})
// Async / await usage
const jsonArray=await csv().fromFile(csvFilePath);
/**
csvStr:
1,2,3
4,5,6
7,8,9
*/
const csv=require('csvtojson')
csv({
noheader:true,
output: "csv"
})
.fromString(csvStr)
.then((csvRow)=>{
console.log(csvRow) // => [["1","2","3"], ["4","5","6"], ["7","8","9"]]
})
const request=require('request')
const csv=require('csvtojson')
csv()
.fromStream(request.get('http://mywebsite.com/mycsvfile.csv'))
.subscribe((json)=>{
return new Promise((resolve,reject)=>{
// long operation for each json e.g. transform / write into database.
})
},onError,onComplete);
/**
csvStr:
a,b,c
1,2,3
4,5,6
*/
const csv=require('csvtojson')
csv({output:"line"})
.fromString(csvStr)
.subscribe((csvLine)=>{
// csvLine => "1,2,3" and "4,5,6"
})
const csv=require('csvtojson');
const readStream=require('fs').createReadStream(csvFilePath);
const writeStream=request.put('http://mysite.com/obj.json');
readStream.pipe(csv()).pipe(writeStream);
To find more detailed usage, please see API section
$ npm i -g csvtojson
$ csvtojson [options] <csv file path>
Convert csv file and save result to json file:
$ csvtojson source.csv > converted.json
Pipe in csv data:
$ cat ./source.csv | csvtojson > converted.json
Print Help:
$ csvtojson
- Parameters
- Asynchronouse Result Process
- Events
- Hook / Transform
- Nested JSON Structure
- Header Row
- Multi CPU Core Support(experimental)
- Column Parser
require('csvtojson')
returns a constructor function which takes 2 arguments:
- parser parameters
- Stream options
const csv=require('csvtojson')
const converter=csv(parserParameters, streamOptions)
Both arguments are optional.
For Stream Options
please read Stream Option from Node.JS
parserParameters
is a JSON object like:
const converter=csv({
noheader:true,
trim:true,
})
Following parameters are supported:
- output: The format to be converted to. "json" (default) -- convert csv to json. "csv" -- convert csv to csv row array. "line" -- convert csv to csv line string
- delimiter: delimiter used for seperating columns. Use "auto" if delimiter is unknown in advance, in this case, delimiter will be auto-detected (by best attempt). Use an array to give a list of potential delimiters e.g. [",","|","$"]. default: ","
- quote: If a column contains delimiter, it is able to use quote character to surround the column content. e.g. "hello, world" wont be split into two columns while parsing. Set to "off" will ignore all quotes. default: " (double quote)
- trim: Indicate if parser trim off spaces surrounding column content. e.g. " content " will be trimmed to "content". Default: true
- checkType: This parameter turns on and off whether check field type. Default is false. (The default is
true
if version < 1.1.4) - ignoreEmpty: Ignore the empty value in CSV columns. If a column value is not given, set this to true to skip them. Default: false.
- fork (experimental): Fork another process to parse the CSV stream. It is effective if many concurrent parsing sessions for large csv files. Default: false
- noheader:Indicating csv data has no header row and first row is data row. Default is false. See header row
- headers: An array to specify the headers of CSV data. If --noheader is false, this value will override CSV header row. Default: null. Example: ["my field","name"]. See header row
- flatKeys: Don't interpret dots (.) and square brackets in header fields as nested object or array identifiers at all (treat them like regular characters for JSON field identifiers). Default: false.
- maxRowLength: the max character a csv row could have. 0 means infinite. If max number exceeded, parser will emit "error" of "row_exceed". if a possibly corrupted csv data provided, give it a number like 65535 so the parser wont consume memory. default: 0
- checkColumn: whether check column number of a row is the same as headers. If column number mismatched headers number, an error of "mismatched_column" will be emitted.. default: false
- eol: End of line character. If omitted, parser will attempt to retrieve it from the first chunks of CSV data.
- escape: escape character used in quoted column. Default is double quote (") according to RFC4108. Change to back slash (\) or other chars for your own case.
- includeColumns: This parameter instructs the parser to include only those columns as specified by the regular expression. Example: /(name|age)/ will parse and include columns whose header contains "name" or "age"
- ignoreColumns: This parameter instructs the parser to ignore columns as specified by the regular expression. Example: /(name|age)/ will ignore columns whose header contains "name" or "age"
- colParser: Allows override parsing logic for a specific column. It accepts a JSON object with fields like:
headName: <String | Function | ColParser>
. e.g. {field1:'number'} will use built-in number parser to convert value of thefield1
column to number. For more information See details below - alwaysSplitAtEOL: Always interpret each line (as defined by
eol
) as a row. This will preventeol
characters from being used within a row (even inside a quoted field). This ensures that misplaced quotes only break on row, and not all ensuing rows.
All parameters can be used in Command Line tool.
Since v2.0.0
, asynchronouse processing has been fully supported.
e.g. Process each JSON result asynchronousely.
csv().fromFile(csvFile)
.subscribe((json)=>{
return new Promise((resolve,reject)=>{
// Async operation on the json
// dont forget to call resolve and reject
})
})
For more details please read:
- Add Promise and Async / Await support
- Add asynchronous line by line processing support
- Async Hooks Support
Converter
class defined a series of events.
header
event is emitted for each CSV file once. It passes an array object which contains the names of the header row.
const csv=require('csvtojson')
csv()
.on('header',(header)=>{
//header=> [header1, header2, header3]
})
header
is always an array of strings without types.
data
event is emitted for each parsed CSV line. It passes buffer of strigified JSON in ndjson format unless objectMode
is set true in stream option.
const csv=require('csvtojson')
csv()
.on('data',(data)=>{
//data is a buffer object
const jsonStr= data.toString('utf8')
})
error
event is emitted if there is any errors happened during parsing.
const csv=require('csvtojson')
csv()
.on('error',(err)=>{
console.log(err)
})
Note that if error
being emitted, the process will stop as node.js will automatically unpipe()
upper-stream and chained down-stream1. This will cause end
event never being emitted because end
event is only emitted when all data being consumed 2. If need to know when parsing finished, use done
event instead of end
.
done
event is emitted either after parsing successfully finished or any error happens. This indicates the processor has stopped.
const csv=require('csvtojson')
csv()
.on('done',(error)=>{
//do some stuff
})
if any error during parsing, it will be passed in callback.
the hook -- preRawData
will be called with csv string passed to parser.
const csv=require('csvtojson')
// synchronouse
csv()
.preRawData((csvRawData)=>{
var newData=csvRawData.replace('some value','another value');
return newData;
})
// asynchronouse
csv()
.preRawData((csvRawData)=>{
return new Promise((resolve,reject)=>{
var newData=csvRawData.replace('some value','another value');
resolve(newData);
})
})
the function is called each time a file line has been parsed in csv stream. the lineIdx
is the file line number in the file starting with 0.
const csv=require('csvtojson')
// synchronouse
csv()
.preFileLine((fileLineString, lineIdx)=>{
if (lineIdx === 2){
return fileLineString.replace('some value','another value')
}
return fileLineString
})
// asynchronouse
csv()
.preFileLine((fileLineString, lineIdx)=>{
return new Promise((resolve,reject)=>{
// async function processing the data.
})
})
To transform result that is sent to downstream, use .subscribe
method for each json populated.
const csv=require('csvtojson')
csv()
.subscribe((jsonObj,index)=>{
jsonObj.myNewKey='some value'
// OR asynchronousely
return new Promise((resolve,reject)=>{
jsonObj.myNewKey='some value';
resolve();
})
})
.on('data',(jsonObj)=>{
console.log(jsonObj.myNewKey) // some value
});
csvtojson
is able to convert csv line to a nested JSON by correctly defining its csv header row. This is default out-of-box feature.
Here is an example. Original CSV:
fieldA.title, fieldA.children.0.name, fieldA.children.0.id,fieldA.children.1.name, fieldA.children.1.employee.0.name,fieldA.children.1.employee.1.name, fieldA.address.0,fieldA.address.1, description
Food Factory, Oscar, 0023, Tikka, Tim, Joe, 3 Lame Road, Grantstown, A fresh new food factory
Kindom Garden, Ceil, 54, Pillow, Amst, Tom, 24 Shaker Street, HelloTown, Awesome castle
The data above contains nested JSON including nested array of JSON objects and plain texts.
Using csvtojson to convert, the result would be like:
[{
"fieldA": {
"title": "Food Factory",
"children": [{
"name": "Oscar",
"id": "0023"
}, {
"name": "Tikka",
"employee": [{
"name": "Tim"
}, {
"name": "Joe"
}]
}],
"address": ["3 Lame Road", "Grantstown"]
},
"description": "A fresh new food factory"
}, {
"fieldA": {
"title": "Kindom Garden",
"children": [{
"name": "Ceil",
"id": "54"
}, {
"name": "Pillow",
"employee": [{
"name": "Amst"
}, {
"name": "Tom"
}]
}],
"address": ["24 Shaker Street", "HelloTown"]
},
"description": "Awesome castle"
}]
In order to not produce nested JSON, simply set flatKeys:true
in parameters.
/**
csvStr:
a.b,a.c
1,2
*/
csv({flatKeys:true})
.fromString(csvStr)
.subscribe((jsonObj)=>{
//{"a.b":1,"a.c":2} rather than {"a":{"b":1,"c":2}}
});
csvtojson
uses csv header row as generator of JSON keys. However, it does not require the csv source containing a header row. There are 4 ways to define header rows:
- First row of csv source. Use first row of csv source as header row. This is default.
- If first row of csv source is header row but it is incorrect and need to be replaced. Use
headers:[]
andnoheader:false
parameters. - If original csv source has no header row but the header definition can be defined. Use
headers:[]
andnoheader:true
parameters. - If original csv source has no header row and the header definition is unknow. Use
noheader:true
. This will automatically addfieldN
header to csv cells
// replace header row (first row) from original source with 'header1, header2'
csv({
noheader: false,
headers: ['header1','header2']
})
// original source has no header row. add 'field1' 'field2' ... 'fieldN' as csv header
csv({
noheader: true
})
// original source has no header row. use 'header1' 'header2' as its header row
csv({
noheader: true,
headers: ['header1','header2']
})
Column Parser
allows writing a custom parser for a column in CSV data.
What is Column Parser
When csvtojson
walks through csv data, it converts value in a cell to something else. For example, if checkType
is true
, csvtojson
will attempt to find a proper type parser according to the cell value. That is, if cell value is "5", a numberParser
will be used and all value under that column will use the numberParser
to transform data.
There are currently following built-in parser:
- string: Convert value to string
- number: Convert value to number
- omit: omit the whole column
This will override types infered from checkType:true
parameter. More built-in parsers will be added as requested in issues page.
Example:
/*csv string
column1,column2
hello,1234
*/
csv({
colParser:{
"column1":"omit",
"column2":"string",
},
checkType:true
})
.fromString(csvString)
.subscribe((jsonObj)=>{
//jsonObj: {column2:"1234"}
})
Sometimes, developers want to define custom parser. It is able to pass a function to specific column in colParser
.
Example:
/*csv data
name, birthday
Joe, 1970-01-01
*/
csv({
colParser:{
"birthday":function(item, head, resultRow, row , colIdx){
/*
item - "1970-01-01"
head - "birthday"
resultRow - {name:"Joe"}
row - ["Joe","1970-01-01"]
colIdx - 1
*/
return new Date(item);
}
}
})
Above example will convert birthday
column into a js Date
object.
the returned value will be used in result JSON object. returning undefined
will not change result JSON object.
It is also able to mark a column as flat
:
/*csv string
person.comment,person.number
hello,1234
*/
csv({
colParser:{
"person.number":{
flat:true,
cellParser: "number" // string or a function
}
}
})
.fromString(csvString)
.subscribe((jsonObj)=>{
//jsonObj: {"person.number":1234,"person":{"comment":"hello"}}
})
Very much appreciate any types of donation and support.
csvtojson
follows github convention for contributions. Here are some steps:
- Fork the repo to your github account
- Checkout code from your github repo to your local machine.
- Make code changes and dont forget add related tests.
- Run
npm test
locally before pushing code back. - Create a Pull Request on github.
- Code review and merge
- Changes will be published to NPM within next version.
Thanks all the contributors
Thank you to all our backers! [Become a backer]
Thank you to all our sponsors! (please ask your company to also support this open source project by becoming a sponsor)
To use csvtojson
in browser is quite simple. There are two ways:
1. Embed script directly into script tag
There is a pre-built script located in browser/csvtojson.min.js
. Simply include that file in a script
tag in index.html
page:
<script src="node_modules/csvtojson/browser/csvtojson.min.js"></script>
<!-- or use cdn -->
<script src="https://cdn.rawgit.com/Keyang/node-csvtojson/d41f44aa/browser/csvtojson.min.js"></script>
then use a global csv
function
<script>
csv({
output: "csv"
})
.fromString("a,b,c\n1,2,3")
.then(function(result){
})
</script>
2. Use webpack or browserify
If a module packager is preferred, just simply require("csvtojson")
:
var csv=require("csvtojson");
// or with import
import * as csv from "csvtojson";
//then use csv as normal