csvtojson

A tool concentrating on converting csv data to JSON with customised parser supporting

npm install csvtojson
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CSV2JSON

All you need nodejs csv to json converter. Support big json data, CLI, server. Easily convert your CSV data to nested JSON object.

IMPORTANT!!

Since version 0.3, the core class of csvtojson has been inheriting from stream.Transform class. Therefore, it will behave like a normal Stream object and CSV features will not be available any more. Now the usage is like:

//Converter Class
var Converter=require("csvtojson").core.Converter;
var fs=require("fs");

var csvFileName="./myCSVFile";
var fileStream=fs.createReadStream(csvFileName);
//new converter instance
var csvConverter=new Converter({constructResult:true});

//end_parsed will be emitted once parsing finished
csvConverter.on("end_parsed",function(jsonObj){
   console.log(jsonObj); //here is your result json object
});

//read from file
fileStream.pipe(csvConverter);

Change Log

version 0.3

  • Removed all dependencies
  • Deprecated applyWebServer
  • Added construct parameter for Converter Class
  • Converter Class now works as a proper stream object

GitHub: https://github.com/Keyang/node-csvtojson

Installation

npm install -g csvtojson

Features

  • Powerful library for you nodejs applications processing csv data.
  • Extremly straight forward
  • Multiple input support: CSV File, Readable Stream, CSV String etc.
  • Highly extendible with your own rules and parsers for outputs.
  • Multiple interfaces (webservice, command line)

Usage

Command Line Tools

csvtojson [ CSVFilePath | StartServer] [port]

Example

csvtojson ./myCSVFile

Or use pipe:

cat myCSVFile | csvtojson

To start a webserver

csvtojson startserver [port]

Default port number is 8801.

WebService

After webserve being initialised, it is able to use http post with CSV data as body. For example, we start web server with default configuration:

csvtojson startserver

And then we use curl to perform a web request:

curl -X POST -d "date,*json*employee.name,*json*employee.age,*json*employee.number,*array*address,*array*address,*jsonarray*employee.key,*jsonarray*employee.key,*omit*id

2012-02-12,Eric,31,51234,Dunno Street,Kilkeny Road,key1,key2,2

2012-03-06,Ted,28,51289,Cambridge Road,Tormore,key3,key4,4" http://127.0.0.1:8801/parseCSV

API

Use csvtojson library to your own project. Import csvtojson to your package.json or install through npm:

npm install csvtojson

Quick Start

The core of the tool is Converter class. It is based on node-csv library (version 0.3.6). Therefore it has all features of node-csv. To start a parse, simply use following code:

//Converter Class
var Converter=require("csvtojson").core.Converter;
var fs=require("fs");

var csvFileName="./myCSVFile";
var fileStream=fs.createReadStream(csvFileName);
//new converter instance
var param={};
var csvConverter=new Converter(param);

//end_parsed will be emitted once parsing finished
csvConverter.on("end_parsed",function(jsonObj){
   console.log(jsonObj); //here is your result json object
});

//read from file
fileStream.pipe(csvConverter);

Params

The parameters for Converter constructor are:

  • constructResult: true/false. Whether to constrcut final json object in memory which will be populated in "end_parsed" event. Set to false if deal with huge csv data. default: true.
  • delimiter: delimiter used for seperating columns. default: ","

Parser

CSVTOJSON allows adding customised parsers which concentrating on what to parse and how to parse. It is the main power of the tool that developer only needs to concentrate on how to deal with the data and other concerns like streaming, memory, web, cli etc are done automatically.

How to add a customised parser:

//Parser Manager
var parserMgr=require("csvtojson").core.parserMgr;

parserMgr.addParser("myParserName",/^\*parserRegExp\*/,function (params){
   var columnTitle=params.head; //params.head be like: *parserRegExp*ColumnName;
   var fieldName=columnTitle.replace(this.regExp, ""); //this.regExp is the regular expression above.
   params.resultRow[fieldName]="Hello my parser"+params.item;
});

parserMgr's addParser function take three parameters:

  1. parser name: the name of your parser. It should be unique.

  2. Regular Expression: It is used to test if a column of CSV data is using this parser. In the example above any column's first row starting with parserRegExp will be using it.

  3. Parse function call back: It is where the parse happens. The converter works row by row and therefore the function will be called each time needs to parse a cell in CSV data.

The parameter of Parse function is a JSON object. It contains following fields:

head: The column's first row's data. It generally contains field information. e.g. arrayitems

item: The data inside current cell. e.g. item1

itemIndex: the index of current cell of a row. e.g. 0

rawRow: the reference of current row in array format. e.g. ["item1", 23 ,"hello"]

resultRow: the reference of result row in JSON format. e.g. {"name":"Joe"}

rowIndex: the index of current row in CSV data. start from 1 since 0 is the head. e.g. 1

resultObject: the reference of result object in JSON format. It always has a field called csvRows which is in Array format. It changes as parsing going on. e.g.

{
   "csvRows":[
      {
          "itemName":"item1",
          "number":10
      },
      {
         "itemName":"item2",
         "number":4
      }
   ]
}

WebServer

It is able to start the web server through code.

var webServer=require("csvtojson").interfaces.web;

var server=webServer.startWebServer({
   "port":"8801",
   "urlPath":"/parseCSV"
});

It will return an expressjs Application. You can add your own web app content there. It will return http.Server object.

Events

Following events are used for Converter class:

  • end_parsed: It is emitted when parsing finished. the callback function will contain the JSON object if constructResult is set to true.
  • record_parsed: it is emitted each time a row has been parsed. The callback function has following parameters: result row JSON object reference, Original row array object reference, row index

To subscribe the event:

//Converter Class
var Converter=require("csvtojson").core.Converter;

//end_parsed will be emitted once parsing finished
csvConverter.on("end_parsed",function(jsonObj){
    console.log(jsonObj); //here is your result json object
});

//record_parsed will be emitted each time a row has been parsed.
csvConverter.on("record_parsed",function(resultRow,rawRow,rowIndex){
   console.log(resultRow); //here is your result json object
});

Default Parsers

There are default parsers in the library they are

Array: For columns head start with "*array*" e.g. "*array*fieldName", this parser will combine cells data with same fieldName to one Array.

Nested JSON: For columns head start with "*json*" e.g. "*json*my.nested.json.structure", this parser will create nested nested JSON structure: my.nested.json

Nested JSON Array: For columns head start with "*jsonarray*" e.g. "*jsonarray*my.items", this parser will create structure like my.items[].

Omitted column: For columns head start with "*omit*" e.g. "*omit*id", the parser will omit the column's data.

Example:

Original data:

date,*json*employee.name,*json*employee.age,*json*employee.number,*array*address,*array*address,*jsonarray*employee.key,*jsonarray*employee.key,*omit*id
2012-02-12,Eric,31,51234,Dunno Street,Kilkeny Road,key1,key2,2
2012-03-06,Ted,28,51289,Cambridge Road,Tormore,key3,key4,4

Output data:

{
   "csvRows": [
      {
         "date": "2012-02-12",
         "employee": {
            "name": "Eric",
            "age": "31",
            "number": "51234",
            "key": [
              "key1",
              "key2"
            ]
          },
          "address": [
            "Dunno Street",
            "Kilkeny Road"
          ]
        },
        {
          "date": "2012-03-06",
          "employee": {
            "name": "Ted",
            "age": "28",
            "number": "51289",
            "key": [
              "key3",
              "key4"
            ]
         },
         "address": [
            "Cambridge Road",
            "Tormore"
         ]
      }
   ]
}

Big CSV File

csvtojson library was designed to accept big csv file converting. To avoid memory consumption, it is recommending to use read stream and write stream.

var Converter=require("csvtojson").core.Converter;
var csvConverter=new Converter({constructResult:false}); // The parameter false will turn off final result construction. It can avoid huge memory consumption while parsing. The trade off is final result will not be populated to end_parsed event.

var readStream=require("fs").createReadStream("inputData.csv");

var writeStream=require("fs").createWriteStream("outpuData.json");

readStream.pipe(csvConverter).pipe(writeStream);

The constructResult:false will tell the constructor not to combine the final result which would drain the memory as progressing. The output is piped directly to writeStream.

Convert Big CSV File with Command line tool

csvtojson command line tool supports streaming in big csv file and stream out json file.

It is very convenient to process any kind of big csv file. It's proved having no issue to proceed csv files over 3,000,000 lines (over 500MB) with memory usage under 30MB.

Once you have installed csvtojson, you could use the tool with command:

csvtojson [path to bigcsvdata] > converted.json

Or if you prefer streaming data in from another application:

cat [path to bigcsvdata] | csvtojson > converted.json

They will do the same job.

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