@turf/meta
Advanced tools
@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.
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);
});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.
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.
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.
Callback for coordEach
Type: Function
Parameters
currentCoord Array<number> The current coordinate being processed.coordIndex number The current index of the coordinate being processed.featureIndex number The current index of the Feature being processed.multiFeatureIndex number The current index of the Multi-Feature being processed.geometryIndex number The current index of the Geometry being processed.Iterate over coordinates in any GeoJSON object, similar to Array.forEach()
Parameters
geojson (FeatureCollection | Feature | Geometry) any GeoJSON objectcallback Function a method that takes (currentCoord, coordIndex, featureIndex, multiFeatureIndex)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 = turf.featureCollection([
turf.point([26, 37], {"foo": "bar"}),
turf.point([36, 53], {"hello": "world"})
]);
turf.coordEach(features, function (currentCoord, coordIndex, featureIndex, multiFeatureIndex, geometryIndex) {
//=currentCoord
//=coordIndex
//=featureIndex
//=multiFeatureIndex
//=geometryIndex
});
Returns void
Reduce coordinates in any GeoJSON object, similar to Array.reduce()
Parameters
geojson (FeatureCollection | Geometry | Feature) any GeoJSON objectcallback Function a method that takes (previousValue, currentCoord, coordIndex)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 = turf.featureCollection([
turf.point([26, 37], {"foo": "bar"}),
turf.point([36, 53], {"hello": "world"})
]);
turf.coordReduce(features, function (previousValue, currentCoord, coordIndex, featureIndex, multiFeatureIndex, geometryIndex) {
//=previousValue
//=currentCoord
//=coordIndex
//=featureIndex
//=multiFeatureIndex
//=geometryIndex
return currentCoord;
});
Returns any The value that results from the reduction.
Callback for coordReduce
The first time the callback function is called, the values provided as arguments depend on whether the reduce method has an initialValue argument.
If an initialValue is provided to the reduce method:
If an initialValue is not provided:
Type: Function
Parameters
previousValue any The accumulated value previously returned in the last invocation
of the callback, or initialValue, if supplied.currentCoord Array<number> The current coordinate being processed.coordIndex number The current index of the coordinate being processed.
Starts at index 0, if an initialValue is provided, and at index 1 otherwise.featureIndex number The current index of the Feature being processed.multiFeatureIndex number The current index of the Multi-Feature being processed.geometryIndex number The current index of the Geometry being processed.Iterate over properties in any GeoJSON object, similar to Array.forEach()
Parameters
geojson (FeatureCollection | Feature) any GeoJSON objectcallback Function a method that takes (currentProperties, featureIndex)Examples
var features = turf.featureCollection([
turf.point([26, 37], {foo: 'bar'}),
turf.point([36, 53], {hello: 'world'})
]);
turf.propEach(features, function (currentProperties, featureIndex) {
//=currentProperties
//=featureIndex
});
Returns void
Callback for propEach
Type: Function
Parameters
currentProperties Object The current Properties being processed.featureIndex number The current index of the Feature being processed.Callback for propReduce
The first time the callback function is called, the values provided as arguments depend on whether the reduce method has an initialValue argument.
If an initialValue is provided to the reduce method:
If an initialValue is not provided:
Type: Function
Parameters
previousValue any The accumulated value previously returned in the last invocation
of the callback, or initialValue, if supplied.currentProperties any The current Properties being processed.featureIndex number The current index of the Feature being processed.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
geojson (FeatureCollection | Feature) any GeoJSON objectcallback Function a method that takes (previousValue, currentProperties, featureIndex)initialValue any? Value to use as the first argument to the first call of the callback.Examples
var features = turf.featureCollection([
turf.point([26, 37], {foo: 'bar'}),
turf.point([36, 53], {hello: 'world'})
]);
turf.propReduce(features, function (previousValue, currentProperties, featureIndex) {
//=previousValue
//=currentProperties
//=featureIndex
return currentProperties
});
Returns any The value that results from the reduction.
Callback for featureEach
Type: Function
Parameters
currentFeature Feature<any> The current Feature being processed.featureIndex number The current index of the Feature being processed.Iterate over features in any GeoJSON object, similar to Array.forEach.
Parameters
geojson (FeatureCollection | Feature | Geometry) any GeoJSON objectcallback Function a method that takes (currentFeature, featureIndex)Examples
var features = turf.featureCollection([
turf.point([26, 37], {foo: 'bar'}),
turf.point([36, 53], {hello: 'world'})
]);
turf.featureEach(features, function (currentFeature, featureIndex) {
//=currentFeature
//=featureIndex
});
Returns void
Callback for featureReduce
The first time the callback function is called, the values provided as arguments depend on whether the reduce method has an initialValue argument.
If an initialValue is provided to the reduce method:
If an initialValue is not provided:
Type: Function
Parameters
previousValue any The accumulated value previously returned in the last invocation
of the callback, or initialValue, if supplied.currentFeature Feature The current Feature being processed.featureIndex number The current index of the Feature being processed.Reduce features in any GeoJSON object, similar to Array.reduce().
Parameters
geojson (FeatureCollection | Feature | Geometry) any GeoJSON objectcallback Function a method that takes (previousValue, currentFeature, featureIndex)initialValue any? Value to use as the first argument to the first call of the callback.Examples
var features = turf.featureCollection([
turf.point([26, 37], {"foo": "bar"}),
turf.point([36, 53], {"hello": "world"})
]);
turf.featureReduce(features, function (previousValue, currentFeature, featureIndex) {
//=previousValue
//=currentFeature
//=featureIndex
return currentFeature
});
Returns any The value that results from the reduction.
Get all coordinates from any GeoJSON object.
Parameters
geojson (FeatureCollection | Feature | Geometry) any GeoJSON objectExamples
var features = turf.featureCollection([
turf.point([26, 37], {foo: 'bar'}),
turf.point([36, 53], {hello: 'world'})
]);
var coords = turf.coordAll(features);
//= [[26, 37], [36, 53]]
Returns Array<Array<number>> coordinate position array
Callback for geomEach
Type: Function
Parameters
currentGeometry Geometry The current Geometry being processed.featureIndex number The current index of the Feature being processed.featureProperties Object The current Feature Properties being processed.featureBBox Array<number> The current Feature BBox being processed.featureId (number | string) The current Feature Id being processed.Iterate over each geometry in any GeoJSON object, similar to Array.forEach()
Parameters
geojson (FeatureCollection | Feature | Geometry) any GeoJSON objectcallback Function a method that takes (currentGeometry, featureIndex, featureProperties, featureBBox, featureId)Examples
var features = turf.featureCollection([
turf.point([26, 37], {foo: 'bar'}),
turf.point([36, 53], {hello: 'world'})
]);
turf.geomEach(features, function (currentGeometry, featureIndex, featureProperties, featureBBox, featureId) {
//=currentGeometry
//=featureIndex
//=featureProperties
//=featureBBox
//=featureId
});
Returns void
Callback for geomReduce
The first time the callback function is called, the values provided as arguments depend on whether the reduce method has an initialValue argument.
If an initialValue is provided to the reduce method:
If an initialValue is not provided:
Type: Function
Parameters
previousValue any The accumulated value previously returned in the last invocation
of the callback, or initialValue, if supplied.currentGeometry Geometry The current Geometry being processed.featureIndex number The current index of the Feature being processed.featureProperties Object The current Feature Properties being processed.featureBBox Array<number> The current Feature BBox being processed.featureId (number | string) The current Feature Id being processed.Reduce geometry in any GeoJSON object, similar to Array.reduce().
Parameters
geojson (FeatureCollection | Feature | Geometry) any GeoJSON objectcallback Function a method that takes (previousValue, currentGeometry, featureIndex, featureProperties, featureBBox, featureId)initialValue any? Value to use as the first argument to the first call of the callback.Examples
var features = turf.featureCollection([
turf.point([26, 37], {foo: 'bar'}),
turf.point([36, 53], {hello: 'world'})
]);
turf.geomReduce(features, function (previousValue, currentGeometry, featureIndex, featureProperties, featureBBox, featureId) {
//=previousValue
//=currentGeometry
//=featureIndex
//=featureProperties
//=featureBBox
//=featureId
return currentGeometry
});
Returns any The value that results from the reduction.
Callback for flattenEach
Type: Function
Parameters
currentFeature Feature The current flattened feature being processed.featureIndex number The current index of the Feature being processed.multiFeatureIndex number The current index of the Multi-Feature being processed.Iterate over flattened features in any GeoJSON object, similar to Array.forEach.
Parameters
geojson (FeatureCollection | Feature | Geometry) any GeoJSON objectcallback Function a method that takes (currentFeature, featureIndex, multiFeatureIndex)Examples
var features = turf.featureCollection([
turf.point([26, 37], {foo: 'bar'}),
turf.multiPoint([[40, 30], [36, 53]], {hello: 'world'})
]);
turf.flattenEach(features, function (currentFeature, featureIndex, multiFeatureIndex) {
//=currentFeature
//=featureIndex
//=multiFeatureIndex
});
Callback for flattenReduce
The first time the callback function is called, the values provided as arguments depend on whether the reduce method has an initialValue argument.
If an initialValue is provided to the reduce method:
If an initialValue is not provided:
Type: Function
Parameters
previousValue any The accumulated value previously returned in the last invocation
of the callback, or initialValue, if supplied.currentFeature Feature The current Feature being processed.featureIndex number The current index of the Feature being processed.multiFeatureIndex number The current index of the Multi-Feature being processed.Reduce flattened features in any GeoJSON object, similar to Array.reduce().
Parameters
geojson (FeatureCollection | Feature | Geometry) any GeoJSON objectcallback Function a method that takes (previousValue, currentFeature, featureIndex, multiFeatureIndex)initialValue any? Value to use as the first argument to the first call of the callback.Examples
var features = turf.featureCollection([
turf.point([26, 37], {foo: 'bar'}),
turf.multiPoint([[40, 30], [36, 53]], {hello: 'world'})
]);
turf.flattenReduce(features, function (previousValue, currentFeature, featureIndex, multiFeatureIndex) {
//=previousValue
//=currentFeature
//=featureIndex
//=multiFeatureIndex
return currentFeature
});
Returns any The value that results from the reduction.
Callback for segmentEach
Type: Function
Parameters
currentSegment Feature<LineString> The current Segment being processed.featureIndex number The current index of the Feature being processed.multiFeatureIndex number The current index of the Multi-Feature being processed.geometryIndex number The current index of the Geometry being processed.segmentIndex number The current index of the Segment being processed.Returns void
Iterate over 2-vertex line segment in any GeoJSON object, similar to Array.forEach() (Multi)Point geometries do not contain segments therefore they are ignored during this operation.
Parameters
geojson (FeatureCollection | Feature | Geometry) any GeoJSONcallback Function a method that takes (currentSegment, featureIndex, multiFeatureIndex, geometryIndex, segmentIndex)Examples
var polygon = turf.polygon([[[-50, 5], [-40, -10], [-50, -10], [-40, 5], [-50, 5]]]);
// Iterate over GeoJSON by 2-vertex segments
turf.segmentEach(polygon, function (currentSegment, featureIndex, multiFeatureIndex, geometryIndex, segmentIndex) {
//=currentSegment
//=featureIndex
//=multiFeatureIndex
//=geometryIndex
//=segmentIndex
});
// Calculate the total number of segments
var total = 0;
turf.segmentEach(polygon, function () {
total++;
});
Returns void
Callback for segmentReduce
The first time the callback function is called, the values provided as arguments depend on whether the reduce method has an initialValue argument.
If an initialValue is provided to the reduce method:
If an initialValue is not provided:
Type: Function
Parameters
previousValue any The accumulated value previously returned in the last invocation
of the callback, or initialValue, if supplied.currentSegment Feature<LineString> The current Segment being processed.featureIndex number The current index of the Feature being processed.multiFeatureIndex number The current index of the Multi-Feature being processed.geometryIndex number The current index of the Geometry being processed.segmentIndex number The current index of the Segment being processed.Reduce 2-vertex line segment in any GeoJSON object, similar to Array.reduce() (Multi)Point geometries do not contain segments therefore they are ignored during this operation.
Parameters
geojson (FeatureCollection | Feature | Geometry) any GeoJSONcallback Function a method that takes (previousValue, currentSegment, currentIndex)initialValue any? Value to use as the first argument to the first call of the callback.Examples
var polygon = turf.polygon([[[-50, 5], [-40, -10], [-50, -10], [-40, 5], [-50, 5]]]);
// Iterate over GeoJSON by 2-vertex segments
turf.segmentReduce(polygon, function (previousSegment, currentSegment, featureIndex, multiFeatureIndex, geometryIndex, segmentIndex) {
//= previousSegment
//= currentSegment
//= featureIndex
//= multiFeatureIndex
//= geometryIndex
//= segmentInex
return currentSegment
});
// Calculate the total number of segments
var initialValue = 0
var total = turf.segmentReduce(polygon, function (previousValue) {
previousValue++;
return previousValue;
}, initialValue);
Returns void
Callback for lineEach
Type: Function
Parameters
currentLine Feature<LineString> The current LineString|LinearRing being processedfeatureIndex number The current index of the Feature being processedmultiFeatureIndex number The current index of the Multi-Feature being processedgeometryIndex number The current index of the Geometry being processedIterate over line or ring coordinates in LineString, Polygon, MultiLineString, MultiPolygon Features or Geometries, similar to Array.forEach.
Parameters
geojson (Geometry | Feature<(LineString | Polygon | MultiLineString | MultiPolygon)>) objectcallback Function a method that takes (currentLine, featureIndex, multiFeatureIndex, geometryIndex)Examples
var multiLine = turf.multiLineString([
[[26, 37], [35, 45]],
[[36, 53], [38, 50], [41, 55]]
]);
turf.lineEach(multiLine, function (currentLine, featureIndex, multiFeatureIndex, geometryIndex) {
//=currentLine
//=featureIndex
//=multiFeatureIndex
//=geometryIndex
});
Callback for lineReduce
The first time the callback function is called, the values provided as arguments depend on whether the reduce method has an initialValue argument.
If an initialValue is provided to the reduce method:
If an initialValue is not provided:
Type: Function
Parameters
previousValue any The accumulated value previously returned in the last invocation
of the callback, or initialValue, if supplied.currentLine Feature<LineString> The current LineString|LinearRing being processed.featureIndex number The current index of the Feature being processedmultiFeatureIndex number The current index of the Multi-Feature being processedgeometryIndex number The current index of the Geometry being processedReduce features in any GeoJSON object, similar to Array.reduce().
Parameters
geojson (Geometry | Feature<(LineString | Polygon | MultiLineString | MultiPolygon)>) objectcallback Function a method that takes (previousValue, currentLine, featureIndex, multiFeatureIndex, geometryIndex)initialValue any? Value to use as the first argument to the first call of the callback.Examples
var multiPoly = turf.multiPolygon([
turf.polygon([[[12,48],[2,41],[24,38],[12,48]], [[9,44],[13,41],[13,45],[9,44]]]),
turf.polygon([[[5, 5], [0, 0], [2, 2], [4, 4], [5, 5]]])
]);
turf.lineReduce(multiPoly, function (previousValue, currentLine, featureIndex, multiFeatureIndex, geometryIndex) {
//=previousValue
//=currentLine
//=featureIndex
//=multiFeatureIndex
//=geometryIndex
return currentLine
});
Returns any The value that results from the reduction.
Finds a particular 2-vertex LineString Segment from a GeoJSON using @turf/meta indexes.
Negative indexes are permitted. Point & MultiPoint will always return null.
Parameters
geojson (FeatureCollection | Feature | Geometry) Any GeoJSON Feature or Geometryoptions Object Optional parameters (optional, default {})
options.featureIndex number Feature Index (optional, default 0)options.multiFeatureIndex number Multi-Feature Index (optional, default 0)options.geometryIndex number Geometry Index (optional, default 0)options.segmentIndex number Segment Index (optional, default 0)options.properties Object Translate Properties to output LineString (optional, default {})options.bbox BBox Translate BBox to output LineString (optional, default {})options.id (number | string) Translate Id to output LineString (optional, default {})Examples
var multiLine = turf.multiLineString([
[[10, 10], [50, 30], [30, 40]],
[[-10, -10], [-50, -30], [-30, -40]]
]);
// First Segment (defaults are 0)
turf.findSegment(multiLine);
// => Feature<LineString<[[10, 10], [50, 30]]>>
// First Segment of 2nd Multi Feature
turf.findSegment(multiLine, {multiFeatureIndex: 1});
// => Feature<LineString<[[-10, -10], [-50, -30]]>>
// Last Segment of Last Multi Feature
turf.findSegment(multiLine, {multiFeatureIndex: -1, segmentIndex: -1});
// => Feature<LineString<[[-50, -30], [-30, -40]]>>
Returns Feature<LineString> 2-vertex GeoJSON Feature LineString
Finds a particular Point from a GeoJSON using @turf/meta indexes.
Negative indexes are permitted.
Parameters
geojson (FeatureCollection | Feature | Geometry) Any GeoJSON Feature or Geometryoptions Object Optional parameters (optional, default {})
options.featureIndex number Feature Index (optional, default 0)options.multiFeatureIndex number Multi-Feature Index (optional, default 0)options.geometryIndex number Geometry Index (optional, default 0)options.coordIndex number Coord Index (optional, default 0)options.properties Object Translate Properties to output Point (optional, default {})options.bbox BBox Translate BBox to output Point (optional, default {})options.id (number | string) Translate Id to output Point (optional, default {})Examples
var multiLine = turf.multiLineString([
[[10, 10], [50, 30], [30, 40]],
[[-10, -10], [-50, -30], [-30, -40]]
]);
// First Segment (defaults are 0)
turf.findPoint(multiLine);
// => Feature<Point<[10, 10]>>
// First Segment of the 2nd Multi-Feature
turf.findPoint(multiLine, {multiFeatureIndex: 1});
// => Feature<Point<[-10, -10]>>
// Last Segment of last Multi-Feature
turf.findPoint(multiLine, {multiFeatureIndex: -1, coordIndex: -1});
// => Feature<Point<[-30, -40]>>
Returns Feature<Point> 2-vertex GeoJSON Feature Point
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.
Install this module individually:
$ npm install @turf/meta
Or install the Turf module that includes it as a function:
$ npm install @turf/turf
6.5.0
@turf/points-with-polygon Add MultiPoint support
(PR https://github.com/Turfjs/turf/pull/2137 - Author @twelch)@turf/dissolve Complete rewrite of the dissolve module to resolve many bugs
(PR https://github.com/Turfjs/turf/pull/2110 - Author @rowanwins)
@turf/mask Complete rewrite of the mask module to resolve many bugs
(PR https://github.com/Turfjs/turf/pull/2130 - Author @rowanwins)
@turf/boolean-valid Add missing dependency to
(PR https://github.com/Turfjs/turf/pull/2094 - Author @rycgar)
@turf/boolean-overlap Improve clarity
(PR https://github.com/Turfjs/turf/pull/2133 - Author @patrickbrett)FAQs
turf meta module
We found that @turf/meta demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 9 open source maintainers collaborating on the project.
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