@turf/meta

Callback for coordEach

Type: Function

• 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()

• geojson (FeatureCollection | Feature | Geometry) any GeoJSON object
• callback 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)

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

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

• 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.

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

• geojson (FeatureCollection | Geometry | Feature) any GeoJSON object
• callback 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)

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 propEach

Type: Function

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

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

• geojson (FeatureCollection | Feature) any GeoJSON object
• callback Function a method that takes (currentProperties, featureIndex)

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 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

• 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.

• geojson (FeatureCollection | Feature) any GeoJSON object
• callback Function a method that takes (previousValue, currentProperties, featureIndex)
• initialValue any? Value to use as the first argument to the first call of the callback.

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

• 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.

• geojson (FeatureCollection | Feature | Geometry) any GeoJSON object
• callback Function a method that takes (currentFeature, featureIndex)

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:

• 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

• 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().

• geojson (FeatureCollection | Feature | Geometry) any GeoJSON object
• callback Function a method that takes (previousValue, currentFeature, featureIndex)
• initialValue any? Value to use as the first argument to the first call of the callback.

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.

• geojson (FeatureCollection | Feature | Geometry) any GeoJSON object

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

• 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()

• geojson (FeatureCollection | Feature | Geometry) any GeoJSON object
• callback Function a method that takes (currentGeometry, featureIndex, featureProperties, featureBBox, featureId)

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:

• 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

• 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().

• geojson (FeatureCollection | Feature | Geometry) any GeoJSON object
• callback 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.

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

• 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.

• geojson (FeatureCollection | Feature | Geometry) any GeoJSON object
• callback Function a method that takes (currentFeature, featureIndex, multiFeatureIndex)

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:

• 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

• 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().

• geojson (FeatureCollection | Feature | Geometry) any GeoJSON object
• callback 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.

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

• 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.

• geojson (FeatureCollection | Feature | Geometry) any GeoJSON
• callback Function a method that takes (currentSegment, featureIndex, multiFeatureIndex, geometryIndex, segmentIndex)

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:

• 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

• 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.

• geojson (FeatureCollection | Feature | Geometry) any GeoJSON
• callback Function a method that takes (previousValue, currentSegment, currentIndex)
• initialValue any? Value to use as the first argument to the first call of the callback.

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 void

Callback for lineEach

Type: Function

• 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

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

• geojson (Geometry | Feature<(LineString | Polygon | MultiLineString | MultiPolygon)>) object
• callback Function a method that takes (currentLine, featureIndex, multiFeatureIndex, geometryIndex)

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:

• 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

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

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

• geojson (Geometry | Feature<(LineString | Polygon | MultiLineString | MultiPolygon)>) object
• callback 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.

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.

• 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 {})

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.

• 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 {})

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 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