@turf/meta

coordEachCallback

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.

Returns void

coordEach

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

Parameters

geojson AllGeoJSON any GeoJSON object
callback coordEachCallback 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

coordReduceCallback

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:

The previousValue argument is initialValue.
The currentValue argument is the value of the first element present in the array.

If an initialValue is not provided:

The previousValue argument is the value of the first element present in the array.
The currentValue argument is the value of the second element present in the array.

Type: Function

Parameters

previousValue Reducer 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.

Returns Reducer

coordReduce

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

Parameters

geojson AllGeoJSON any GeoJSON object
callback coordReduceCallback a method that takes (previousValue, currentCoord, coordIndex)
initialValue Reducer? 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 Reducer The value that results from the reduction.

propEachCallback

Callback for propEach

Type: Function

Parameters

currentProperties GeoJsonProperties The current Properties being processed.
featureIndex number The current index of the Feature being processed.

Returns void

propEach

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

Parameters

geojson (FeatureCollection | Feature) any GeoJSON object
callback propEachCallback 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

propReduceCallback

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:

The previousValue argument is initialValue.
The currentValue argument is the value of the first element present in the array.

If an initialValue is not provided:

The previousValue argument is the value of the first element present in the array.
The currentValue argument is the value of the second element present in the array.

Type: Function

Parameters

previousValue Reducer The accumulated value previously returned in the last invocation of the callback, or initialValue, if supplied.
currentProperties GeoJsonProperties The current Properties being processed.
featureIndex number The current index of the Feature being processed.

Returns Reducer

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

geojson (FeatureCollection | Feature | Geometry) any GeoJSON object
callback propReduceCallback a method that takes (previousValue, currentProperties, featureIndex)
initialValue Reducer? 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 Reducer The value that results from the reduction.

featureEachCallback

Callback for featureEach

Type: Function

Parameters

currentFeature Feature<any> The current Feature being processed.
featureIndex number The current index of the Feature being processed.

Returns void

featureEach

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

Parameters

geojson (FeatureCollection | Feature | Feature<GeometryCollection>) any GeoJSON object
callback featureEachCallback 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

featureReduceCallback

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:

The previousValue argument is initialValue.
The currentValue argument is the value of the first element present in the array.

If an initialValue is not provided:

The previousValue argument is the value of the first element present in the array.
The currentValue argument is the value of the second element present in the array.

Type: Function

Parameters

previousValue Reducer 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.

Returns Reducer

featureReduce

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

Parameters

geojson (FeatureCollection | Feature | Feature<GeometryCollection>) any GeoJSON object
callback featureReduceCallback a method that takes (previousValue, currentFeature, featureIndex)
initialValue Reducer? 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 Reducer The value that results from the reduction.

coordAll

Get all coordinates from any GeoJSON object.

Parameters

geojson AllGeoJSON any GeoJSON object

Examples

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

geomEachCallback

Callback for geomEach

Type: Function

Parameters

currentGeometry GeometryObject The current Geometry being processed.
featureIndex number The current index of the Feature being processed.
featureProperties GeoJsonProperties The current Feature Properties being processed.
featureBBox BBox The current Feature BBox being processed.
featureId Id The current Feature Id being processed.

Returns void

geomEach

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

Parameters

geojson (FeatureCollection | Feature | Geometry | GeometryObject | Feature<GeometryCollection>) any GeoJSON object
callback geomEachCallback 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

geomReduceCallback

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:

The previousValue argument is initialValue.
The currentValue argument is the value of the first element present in the array.

If an initialValue is not provided:

The previousValue argument is the value of the first element present in the array.
The currentValue argument is the value of the second element present in the array.

Type: Function

Parameters

previousValue Reducer The accumulated value previously returned in the last invocation of the callback, or initialValue, if supplied.
currentGeometry GeometryObject The current Geometry being processed.
featureIndex number The current index of the Feature being processed.
featureProperties GeoJsonProperties The current Feature Properties being processed.
featureBBox BBox The current Feature BBox being processed.
featureId Id The current Feature Id being processed.

Returns Reducer

geomReduce

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

Parameters

geojson (FeatureCollection | Feature | GeometryObject | GeometryCollection | Feature<GeometryCollection>) any GeoJSON object
callback geomReduceCallback a method that takes (previousValue, currentGeometry, featureIndex, featureProperties, featureBBox, featureId)
initialValue Reducer? 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 Reducer The value that results from the reduction.

flattenEachCallback

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.

Returns void

flattenEach

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

Parameters

geojson (FeatureCollection | Feature | GeometryObject | GeometryCollection | Feature<GeometryCollection>) any GeoJSON object
callback flattenEachCallback 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
});

Returns void

flattenReduceCallback

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:

The previousValue argument is initialValue.
The currentValue argument is the value of the first element present in the array.

If an initialValue is not provided:

The previousValue argument is the value of the first element present in the array.
The currentValue argument is the value of the second element present in the array.

Type: Function

Parameters

previousValue Reducer 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.

Returns Reducer

flattenReduce

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

Parameters

geojson (FeatureCollection | Feature | GeometryObject | GeometryCollection | Feature<GeometryCollection>) any GeoJSON object
callback flattenReduceCallback a method that takes (previousValue, currentFeature, featureIndex, multiFeatureIndex)
initialValue Reducer? 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 Reducer The value that results from the reduction.

segmentEachCallback

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

segmentEach

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 AllGeoJSON any GeoJSON
callback segmentEachCallback 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

segmentReduceCallback

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:

The previousValue argument is initialValue.
The currentValue argument is the value of the first element present in the array.

If an initialValue is not provided:

The previousValue argument is the value of the first element present in the array.
The currentValue argument is the value of the second element present in the array.

Type: Function

Parameters

previousValue Reducer 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.

Returns Reducer

segmentReduce

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 GeoJSON
callback segmentReduceCallback a method that takes (previousValue, currentSegment, currentIndex)
initialValue Reducer? 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
  //= segmentIndex
  return currentSegment
});

// Calculate the total number of segments
var initialValue = 0
var total = turf.segmentReduce(polygon, function (previousValue) {
    previousValue++;
    return previousValue;
}, initialValue);

Returns Reducer

lineEachCallback

Callback for lineEach

Type: Function

Parameters

currentLine Feature<LineString> The current LineString|LinearRing 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

Returns void

lineEach

Iterate over line or ring coordinates in LineString, Polygon, MultiLineString, MultiPolygon Features or Geometries, similar to Array.forEach.

Parameters

geojson (FeatureCollection<Lines> | Feature<Lines> | Lines | Feature<GeometryCollection> | GeometryCollection) object
callback lineEachCallback 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
});

Returns void

lineReduceCallback

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:

The previousValue argument is initialValue.
The currentValue argument is the value of the first element present in the array.

If an initialValue is not provided:

The previousValue argument is the value of the first element present in the array.
The currentValue argument is the value of the second element present in the array.

Type: Function

Parameters

previousValue Reducer 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 processed
multiFeatureIndex number The current index of the Multi-Feature being processed
geometryIndex number The current index of the Geometry being processed

Returns Reducer

lineReduce

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

Parameters

geojson (FeatureCollection<Lines> | Feature<Lines> | Lines | Feature<GeometryCollection> | GeometryCollection) object
callback Function a method that takes (previousValue, currentLine, featureIndex, multiFeatureIndex, geometryIndex)
initialValue Reducer? 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 Reducer The value that results from the reduction.

findSegment

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 Geometry
options 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

findPoint

Finds a particular Point from a GeoJSON using @turf/meta indexes.

Negative indexes are permitted.

Parameters

geojson (FeatureCollection | Feature | Geometry) Any GeoJSON Feature or Geometry
options 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.

Installation

Install this single module individually:

$ npm install @turf/meta

Or install the all-encompassing @turf/turf module that includes all modules as functions:

$ npm install @turf/turf