@turf/meta

What is @turf/meta?

@turf/meta is a module of the Turf.js library that provides utility functions for working with GeoJSON data. It allows you to iterate over various GeoJSON objects, extract specific properties, and manipulate geometries.

What are @turf/meta's main functionalities?

coordEach

The `coordEach` function iterates over each coordinate in any GeoJSON object, allowing you to perform operations on each coordinate.

const turf = require('@turf/meta');
const point = { "type": "Feature", "geometry": { "type": "Point", "coordinates": [110, 50] } };
turf.coordEach(point, function (coord) {
  console.log(coord);
});

propEach

The `propEach` function iterates over properties in any GeoJSON Feature or FeatureCollection, allowing you to access and manipulate properties.

const turf = require('@turf/meta');
const featureCollection = { "type": "FeatureCollection", "features": [ { "type": "Feature", "properties": { "name": "A" }, "geometry": { "type": "Point", "coordinates": [110, 50] } } ] };
turf.propEach(featureCollection, function (properties, featureIndex) {
  console.log(properties);
});

geomEach

The `geomEach` function iterates over each geometry in any GeoJSON object, allowing you to perform operations on each geometry.

const turf = require('@turf/meta');
const featureCollection = { "type": "FeatureCollection", "features": [ { "type": "Feature", "geometry": { "type": "Point", "coordinates": [110, 50] } } ] };
turf.geomEach(featureCollection, function (geometry, featureIndex) {
  console.log(geometry);
});

Other packages similar to @turf/meta

geojson-utils

The `geojson-utils` package provides utility functions for manipulating and analyzing GeoJSON data. It offers similar functionalities to @turf/meta, such as iterating over coordinates and geometries, but it also includes additional features like distance calculations and point-in-polygon tests.

geolib

The `geolib` package is a library for geospatial calculations. While it does not focus specifically on GeoJSON, it provides a wide range of geospatial utilities, including distance calculations, bounding box operations, and coordinate transformations. It can be used in conjunction with GeoJSON data for various geospatial tasks.

geojson-extent

The `geojson-extent` package is designed to calculate the bounding box of GeoJSON objects. While it does not offer the same breadth of functionality as @turf/meta, it is useful for specific tasks related to determining the spatial extent of GeoJSON data.

README

@turf/meta

coordEach

Iterate over coordinates in any GeoJSON object, similar to Array.forEach()

Parameters

• layer Object any GeoJSON object
• callback Function a method that takes (currentCoords, currentIndex)
• excludeWrapCoord [boolean] whether or not to include the final coordinate of LinearRings that wraps the ring in its iteration. (optional, default false)

Examples

var features = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [26, 37]
      }
    },
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [36, 53]
      }
    }
  ]
};
turf.coordEach(features, function (currentCoords, currentIndex) {
  //=currentCoords
  //=currentIndex
});

coordReduce

Reduce coordinates in any GeoJSON object, similar to Array.reduce()

Parameters

• layer Object any GeoJSON object
• callback Function a method that takes (previousValue, currentCoords, currentIndex)
• initialValue [Any] Value to use as the first argument to the first call of the callback.
• excludeWrapCoord [boolean] whether or not to include the final coordinate of LinearRings that wraps the ring in its iteration. (optional, default false)

Examples

var features = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [26, 37]
      }
    },
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [36, 53]
      }
    }
  ]
};
turf.coordReduce(features, function (previousValue, currentCoords, currentIndex) {
  //=previousValue
  //=currentCoords
  //=currentIndex
  return currentCoords;
});

Returns Any The value that results from the reduction.

propEach

Iterate over properties in any GeoJSON object, similar to Array.forEach()

Parameters

• layer Object any GeoJSON object
• callback Function a method that takes (currentProperties, currentIndex)

Examples

var features = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {"foo": "bar"},
      "geometry": {
        "type": "Point",
        "coordinates": [26, 37]
      }
    },
    {
      "type": "Feature",
      "properties": {"hello": "world"},
      "geometry": {
        "type": "Point",
        "coordinates": [36, 53]
      }
    }
  ]
};
turf.propEach(features, function (currentProperties, currentIndex) {
  //=currentProperties
  //=currentIndex
});

propReduce

Reduce properties in any GeoJSON object into a single value, similar to how Array.reduce works. However, in this case we lazily run the reduction, so an array of all properties is unnecessary.

Parameters

• layer Object any GeoJSON object
• callback Function a method that takes (previousValue, currentProperties, currentIndex)
• initialValue [Any] Value to use as the first argument to the first call of the callback.

Examples

var features = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {"foo": "bar"},
      "geometry": {
        "type": "Point",
        "coordinates": [26, 37]
      }
    },
    {
      "type": "Feature",
      "properties": {"hello": "world"},
      "geometry": {
        "type": "Point",
        "coordinates": [36, 53]
      }
    }
  ]
};
turf.propReduce(features, function (previousValue, currentProperties, currentIndex) {
  //=previousValue
  //=currentProperties
  //=currentIndex
  return currentProperties
});

Returns Any The value that results from the reduction.

featureEach

Iterate over features in any GeoJSON object, similar to Array.forEach.

Parameters

• layer Object any GeoJSON object
• callback Function a method that takes (currentFeature, currentIndex)

Examples

var features = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [26, 37]
      }
    },
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [36, 53]
      }
    }
  ]
};
turf.featureEach(features, function (currentFeature, currentIndex) {
  //=currentFeature
  //=currentIndex
});

featureReduce

Reduce features in any GeoJSON object, similar to Array.reduce().

Parameters

• layer Object any GeoJSON object
• callback Function a method that takes (previousValue, currentFeature, currentIndex)
• initialValue [Any] Value to use as the first argument to the first call of the callback.

Examples

var features = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {"foo": "bar"},
      "geometry": {
        "type": "Point",
        "coordinates": [26, 37]
      }
    },
    {
      "type": "Feature",
      "properties": {"hello": "world"},
      "geometry": {
        "type": "Point",
        "coordinates": [36, 53]
      }
    }
  ]
};
turf.featureReduce(features, function (previousValue, currentFeature, currentIndex) {
  //=previousValue
  //=currentFeature
  //=currentIndex
  return currentFeature
});

Returns Any The value that results from the reduction.

coordAll

Get all coordinates from any GeoJSON object.

Parameters

• layer Object any GeoJSON object

Examples

var features = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [26, 37]
      }
    },
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [36, 53]
      }
    }
  ]
};
var coords = turf.coordAll(features);
//=coords

Returns Array<Array<number>> coordinate position array

geomEach

Iterate over each geometry in any GeoJSON object, similar to Array.forEach()

Parameters

• layer Object any GeoJSON object
• callback Function a method that takes (currentGeometry, currentIndex)

Examples

var features = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [26, 37]
      }
    },
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Point",
        "coordinates": [36, 53]
      }
    }
  ]
};
turf.geomEach(features, function (currentGeometry, currentIndex) {
  //=currentGeometry
  //=currentIndex
});

geomReduce

Reduce geometry in any GeoJSON object, similar to Array.reduce().

Parameters

• layer Object any GeoJSON object
• callback Function a method that takes (previousValue, currentGeometry, currentIndex)
• initialValue [Any] Value to use as the first argument to the first call of the callback.

Examples

var features = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {"foo": "bar"},
      "geometry": {
        "type": "Point",
        "coordinates": [26, 37]
      }
    },
    {
      "type": "Feature",
      "properties": {"hello": "world"},
      "geometry": {
        "type": "Point",
        "coordinates": [36, 53]
      }
    }
  ]
};
turf.geomReduce(features, function (previousValue, currentGeometry, currentIndex) {
  //=previousValue
  //=currentGeometry
  //=currentIndex
  return currentGeometry
});

Returns Any The value that results from the reduction.

---

This module is part of the Turfjs project, an open source module collection dedicated to geographic algorithms. It is maintained in the Turfjs/turf repository, where you can create PRs and issues.

Installation

Install this module individually:

$ npm install @turf/meta

Or install the Turf module that includes it as a function:

$ npm install @turf/turf