DelimitedFileReader

A promise enabled, ES6 Class for reading delimited text files and emitting the records as objects.

Synopsis

Read the given file, listen to the various events to get the data:

const DelimitedFileReader = require('delimited-file-reader');
 
let fileReader = new DelimitedFileReader(',');
 
fileReader.on('comment', (comment) => {
    console.log(`comment: ${comment}`);
});
 
fileReader.on('data', (data) => {
    console.log(`data: ${JSON.stringify(data)}`);
});
 
fileReader.on('close', () => {
    console.log('Elvis has left the building!');
});
 
// The parse method takes a string filename or a read stream as an argument.
fileReader.parse('./simple-example.csv');
 
 
// comment: # Example file using comma delimited format with comments
// data: {"field_0":"value1-1","field_1":"value2-2"}
// data: {"field_0":"value2-1","field_1":"value2-2"}
// Elvis has left the building!

This code comes from the provided example file: simple-example.js

Description

This class is a simple implementation of a delimited text file reader. The following are configurable.

• column delimiter - Any string or regular expression can be configured
• field names - Define the property names for each column or let the class name it. The class uses the naming convention field_${col_index}.
• comment delimter - Define a string when found at the beginning of a line, defines the line as a comment. This feature can be disabled.

In simpler terms:

• I have a delimited text file or stream with lf or lf\cr as record delimiters.
• The column delimiter can be expressed as a string or regular expresssion.
• They're may be comments in the file using a defined string in the starting position.
• I want to read the file and process each record as an object.
• I may want to name the properties of each object or I may let the class name them.

Project Features

• ES6 Class
• Promise enabled
• Complete test coverage with Mocha and Chai
• JSDoc generated API documentation
• Rest parameters are used for maximum flexibility.

Installation

npm install delimited-file-reader --save

Git Repository: https://github.com/wildbillh/delimited-file-reader

Documentation

There is JSDOC documentation provided: DelimitedFileReader.html

Methods

Constructor

constructor(delimiter = /[,]/, fields = [], commentChar = '#')

The constructor takes three defaulted parameters:

1. delimiter - defaults to a common. Can be any valid string or regular expresssion.
2. fields - defaults to an empty array. In this case, the class will generated field names. The user can also supply an array of strings.
3. commentChar - The string to use to designate a comment line (if it occurs at position 0). Set this to null of the feature should be disabled.

parse

parse(filename)

This method starts the process of reading the files and emitting events. Prior to calling this method, the desired event listeners should be instantiated.

Events

• close - File reading is complete and all records have been emitted.
• comment - A comment was encountered. The entire line is returned.
• data - Contains an object representing the record.
• error - Contains the error message.
• invalid - A record was encountered with the wrong number of fields. This can only occur if the user specifies field names. The entire line is returned.

Author: Bill Hodges