shapefile

What is shapefile?

The shapefile npm package is used for reading and parsing shapefiles, which are a popular geospatial vector data format for geographic information system (GIS) software. This package allows you to read shapefiles and convert them into GeoJSON format, making it easier to work with geospatial data in JavaScript applications.

What are shapefile's main functionalities?

Reading Shapefiles

This feature allows you to read a shapefile and log its contents. The code opens a shapefile, reads its records, and logs each record to the console.

const shapefile = require('shapefile');

shapefile.open("path/to/shapefile.shp")
  .then(source => source.read()
    .then(function log(result) {
      if (result.done) return;
      console.log(result.value);
      return source.read().then(log);
    }))
  .catch(error => console.error(error));

Converting Shapefiles to GeoJSON

This feature allows you to convert a shapefile directly to GeoJSON format. The code reads a shapefile and converts its contents to GeoJSON, which is then logged to the console.

const shapefile = require('shapefile');

shapefile.read("path/to/shapefile.shp")
  .then(geojson => console.log(JSON.stringify(geojson)))
  .catch(error => console.error(error));

Other packages similar to shapefile

shpjs

shpjs is a JavaScript library for reading shapefiles in the browser. It can read both .shp and .dbf files and convert them to GeoJSON. Compared to shapefile, shpjs is more focused on client-side usage and is suitable for web applications that need to handle shapefiles directly in the browser.

terraformer

Terraformer is a modular toolkit for working with geographic data in JavaScript. It includes tools for reading and writing GeoJSON, as well as converting between different geospatial formats. While it does not specifically focus on shapefiles, it provides a broader set of tools for geospatial data manipulation compared to shapefile.

gdal

gdal (Geospatial Data Abstraction Library) is a powerful library for reading and writing raster and vector geospatial data formats. The gdal npm package provides bindings to the GDAL library, allowing you to work with a wide range of geospatial data formats, including shapefiles. It is more comprehensive and feature-rich compared to shapefile, but also more complex to use.

README

Streaming Shapefile Parser

Based on the ESRI Shapefile Technical Description and dBASE Table File Format.

Caveat emptor: this library is a work in progress and does not currently support all shapefile geometry types (see shp.js for details). It also only supports dBASE III and has no error checking. Please contribute if you want to help!

Reading a Shapefile

# shapefile.read(filename[, options], callback)

A convenience API for reading an entire shapefile in one go. Use this method if you don’t mind putting the whole shapefile in memory; use reader instead if you want to process records individually. The specified callback with two arguments:

• error - the error, if any
• collection - a GeoJSON feature collection

The collection has a bbox property containing representing the bounding box of all records in this shapefile. The bounding box is specified as [xmin, ymin, xmax, ymax], where x and y represent longitude and latitude in spherical coordinates.

Streaming a Shapefile

# shapefile.reader(filename[, options])

The main API for reading a shapefile. The supported options are:

• encoding - the DBF encoding (defaults to ISO-8859-1)
• ignore-properties - if true, don’t read properties (faster; defaults to false)

This method returns a reader object.

# reader.readHeader(callback)

Reads the shapefile header, invoking the specified callback with two arguments:

• error - the error, if any
• header - the header object

The header object is simply an object with a bbox property representing the bounding box of all records in this shapefile. The bounding box is specified as [xmin, ymin, xmax, ymax], where x and y represent longitude and latitude in spherical coordinates.

# reader.readRecord(callback)

Reads the next shapefile record, invoking the specified callback with two arguments:

• error - the error, if any
• record - the record object, or shapefile.end

The record object is a GeoJSON feature. (GeoJSON objects are the standard representation of geometry in JavaScript, and they are convenient. If you want to access the shapefile primitives directly, use the private shp and dbf classes instead.)

If there are no more records in this shapefile, the record is the special value shapefile.end.

# reader.close(callback)

Closes the underlying files for this reader. You should call this when you are done reading. If an error occurs during readHeader or readRecord, the reader will be closed automatically.

# shapefile.end

A sentinel value used readRecord to indicate that the end of the file has been reached, and no more records are available. (Note that if the end of file is reached when readHeader is called, this is considered an error because the header is required by the shapefile format.)