# @turf/meta ## coordEachCallback Callback for coordEach Type: [Function][1] **Parameters** - `currentCoord` **[Array][2]<[number][3]>** The current coordinate being processed. - `coordIndex` **[number][3]** The current index of the coordinate being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed. - `multiFeatureIndex` **[number][3]** The current index of the Multi-Feature being processed. - `geometryIndex` **[number][3]** The current index of the Geometry being processed. ## coordEach Iterate over coordinates in any GeoJSON object, similar to Array.forEach() **Parameters** - `geojson` **([FeatureCollection][4] \| [Feature][5] \| [Geometry][6])** any GeoJSON object - `callback` **[Function][1]** a method that takes (currentCoord, coordIndex, featureIndex, multiFeatureIndex) - `excludeWrapCoord` **[boolean][7]** whether or not to include the final coordinate of LinearRings that wraps the ring in its iteration. (optional, default `false`) **Examples** ```javascript 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** ## coordReduce Reduce coordinates in any GeoJSON object, similar to Array.reduce() **Parameters** - `geojson` **([FeatureCollection][4] \| [Geometry][6] \| [Feature][5])** any GeoJSON object - `callback` **[Function][1]** 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][7]** whether or not to include the final coordinate of LinearRings that wraps the ring in its iteration. (optional, default `false`) **Examples** ```javascript 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. ## 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][1] **Parameters** - `previousValue` **any** The accumulated value previously returned in the last invocation of the callback, or initialValue, if supplied. - `currentCoord` **[Array][2]<[number][3]>** The current coordinate being processed. - `coordIndex` **[number][3]** The current index of the coordinate being processed. Starts at index 0, if an initialValue is provided, and at index 1 otherwise. - `featureIndex` **[number][3]** The current index of the Feature being processed. - `multiFeatureIndex` **[number][3]** The current index of the Multi-Feature being processed. - `geometryIndex` **[number][3]** The current index of the Geometry being processed. ## propEach Iterate over properties in any GeoJSON object, similar to Array.forEach() **Parameters** - `geojson` **([FeatureCollection][4] \| [Feature][5])** any GeoJSON object - `callback` **[Function][1]** a method that takes (currentProperties, featureIndex) **Examples** ```javascript 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** ## propEachCallback Callback for propEach Type: [Function][1] **Parameters** - `currentProperties` **[Object][8]** The current Properties being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed. ## 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][1] **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][3]** The current index of the Feature being processed. ## 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][4] \| [Feature][5])** any GeoJSON object - `callback` **[Function][1]** a method that takes (previousValue, currentProperties, featureIndex) - `initialValue` **any?** Value to use as the first argument to the first call of the callback. **Examples** ```javascript 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. ## featureEachCallback Callback for featureEach Type: [Function][1] **Parameters** - `currentFeature` **[Feature][5]<any>** The current Feature being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed. ## featureEach Iterate over features in any GeoJSON object, similar to Array.forEach. **Parameters** - `geojson` **([FeatureCollection][4] \| [Feature][5] \| [Geometry][6])** any GeoJSON object - `callback` **[Function][1]** a method that takes (currentFeature, featureIndex) **Examples** ```javascript 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][1] **Parameters** - `previousValue` **any** The accumulated value previously returned in the last invocation of the callback, or initialValue, if supplied. - `currentFeature` **[Feature][5]** The current Feature being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed. ## featureReduce Reduce features in any GeoJSON object, similar to Array.reduce(). **Parameters** - `geojson` **([FeatureCollection][4] \| [Feature][5] \| [Geometry][6])** any GeoJSON object - `callback` **[Function][1]** a method that takes (previousValue, currentFeature, featureIndex) - `initialValue` **any?** Value to use as the first argument to the first call of the callback. **Examples** ```javascript 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. ## coordAll Get all coordinates from any GeoJSON object. **Parameters** - `geojson` **([FeatureCollection][4] \| [Feature][5] \| [Geometry][6])** any GeoJSON object **Examples** ```javascript 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][2]<[Array][2]<[number][3]>>** coordinate position array ## geomEachCallback Callback for geomEach Type: [Function][1] **Parameters** - `currentGeometry` **[Geometry][6]** The current Geometry being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed. - `featureProperties` **[Object][8]** The current Feature Properties being processed. - `featureBBox` **[Array][2]<[number][3]>** The current Feature BBox being processed. - `featureId` **([number][3] \| [string][9])** The current Feature Id being processed. ## geomEach Iterate over each geometry in any GeoJSON object, similar to Array.forEach() **Parameters** - `geojson` **([FeatureCollection][4] \| [Feature][5] \| [Geometry][6])** any GeoJSON object - `callback` **[Function][1]** a method that takes (currentGeometry, featureIndex, featureProperties, featureBBox, featureId) **Examples** ```javascript 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][1] **Parameters** - `previousValue` **any** The accumulated value previously returned in the last invocation of the callback, or initialValue, if supplied. - `currentGeometry` **[Geometry][6]** The current Geometry being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed. - `featureProperties` **[Object][8]** The current Feature Properties being processed. - `featureBBox` **[Array][2]<[number][3]>** The current Feature BBox being processed. - `featureId` **([number][3] \| [string][9])** The current Feature Id being processed. ## geomReduce Reduce geometry in any GeoJSON object, similar to Array.reduce(). **Parameters** - `geojson` **([FeatureCollection][4] \| [Feature][5] \| [Geometry][6])** any GeoJSON object - `callback` **[Function][1]** 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** ```javascript 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. ## flattenEachCallback Callback for flattenEach Type: [Function][1] **Parameters** - `currentFeature` **[Feature][5]** The current flattened feature being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed. - `multiFeatureIndex` **[number][3]** The current index of the Multi-Feature being processed. ## flattenEach Iterate over flattened features in any GeoJSON object, similar to Array.forEach. **Parameters** - `geojson` **([FeatureCollection][4] \| [Feature][5] \| [Geometry][6])** any GeoJSON object - `callback` **[Function][1]** a method that takes (currentFeature, featureIndex, multiFeatureIndex) **Examples** ```javascript 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 }); ``` ## 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][1] **Parameters** - `previousValue` **any** The accumulated value previously returned in the last invocation of the callback, or initialValue, if supplied. - `currentFeature` **[Feature][5]** The current Feature being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed. - `multiFeatureIndex` **[number][3]** The current index of the Multi-Feature being processed. ## flattenReduce Reduce flattened features in any GeoJSON object, similar to Array.reduce(). **Parameters** - `geojson` **([FeatureCollection][4] \| [Feature][5] \| [Geometry][6])** any GeoJSON object - `callback` **[Function][1]** 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** ```javascript 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. ## segmentEachCallback Callback for segmentEach Type: [Function][1] **Parameters** - `currentSegment` **[Feature][5]<[LineString][10]>** The current Segment being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed. - `multiFeatureIndex` **[number][3]** The current index of the Multi-Feature being processed. - `geometryIndex` **[number][3]** The current index of the Geometry being processed. - `segmentIndex` **[number][3]** 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` **([FeatureCollection][4] \| [Feature][5] \| [Geometry][6])** any GeoJSON - `callback` **[Function][1]** a method that takes (currentSegment, featureIndex, multiFeatureIndex, geometryIndex, segmentIndex) **Examples** ```javascript 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][1] **Parameters** - `previousValue` **any** The accumulated value previously returned in the last invocation of the callback, or initialValue, if supplied. - `currentSegment` **[Feature][5]<[LineString][10]>** The current Segment being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed. - `multiFeatureIndex` **[number][3]** The current index of the Multi-Feature being processed. - `geometryIndex` **[number][3]** The current index of the Geometry being processed. - `segmentIndex` **[number][3]** The current index of the Segment being processed. ## 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][4] \| [Feature][5] \| [Geometry][6])** any GeoJSON - `callback` **[Function][1]** a method that takes (previousValue, currentSegment, currentIndex) - `initialValue` **any?** Value to use as the first argument to the first call of the callback. **Examples** ```javascript 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** ## lineEachCallback Callback for lineEach Type: [Function][1] **Parameters** - `currentLine` **[Feature][5]<[LineString][10]>** The current LineString|LinearRing being processed - `featureIndex` **[number][3]** The current index of the Feature being processed - `multiFeatureIndex` **[number][3]** The current index of the Multi-Feature being processed - `geometryIndex` **[number][3]** The current index of the Geometry being processed ## lineEach Iterate over line or ring coordinates in LineString, Polygon, MultiLineString, MultiPolygon Features or Geometries, similar to Array.forEach. **Parameters** - `geojson` **([Geometry][6] \| [Feature][5]<([LineString][10] \| [Polygon][11] \| [MultiLineString][12] \| [MultiPolygon][13])>)** object - `callback` **[Function][1]** a method that takes (currentLine, featureIndex, multiFeatureIndex, geometryIndex) **Examples** ```javascript 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 }); ``` ## 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][1] **Parameters** - `previousValue` **any** The accumulated value previously returned in the last invocation of the callback, or initialValue, if supplied. - `currentLine` **[Feature][5]<[LineString][10]>** The current LineString|LinearRing being processed. - `featureIndex` **[number][3]** The current index of the Feature being processed - `multiFeatureIndex` **[number][3]** The current index of the Multi-Feature being processed - `geometryIndex` **[number][3]** The current index of the Geometry being processed ## lineReduce Reduce features in any GeoJSON object, similar to Array.reduce(). **Parameters** - `geojson` **([Geometry][6] \| [Feature][5]<([LineString][10] \| [Polygon][11] \| [MultiLineString][12] \| [MultiPolygon][13])>)** object - `callback` **[Function][1]** 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** ```javascript 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. ## 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][4] \| [Feature][5] \| [Geometry][6])** Any GeoJSON Feature or Geometry - `options` **[Object][8]** Optional parameters (optional, default `{}`) - `options.featureIndex` **[number][3]** Feature Index (optional, default `0`) - `options.multiFeatureIndex` **[number][3]** Multi-Feature Index (optional, default `0`) - `options.geometryIndex` **[number][3]** Geometry Index (optional, default `0`) - `options.segmentIndex` **[number][3]** Segment Index (optional, default `0`) - `options.properties` **[Object][8]** Translate Properties to output LineString (optional, default `{}`) - `options.bbox` **[BBox][14]** Translate BBox to output LineString (optional, default `{}`) - `options.id` **([number][3] \| [string][9])** Translate Id to output LineString (optional, default `{}`) **Examples** ```javascript 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> // First Segment of 2nd Multi Feature turf.findSegment(multiLine, {multiFeatureIndex: 1}); // => Feature> // Last Segment of Last Multi Feature turf.findSegment(multiLine, {multiFeatureIndex: -1, segmentIndex: -1}); // => Feature> ``` Returns **[Feature][5]<[LineString][10]>** 2-vertex GeoJSON Feature LineString ## findPoint Finds a particular Point from a GeoJSON using `@turf/meta` indexes. Negative indexes are permitted. **Parameters** - `geojson` **([FeatureCollection][4] \| [Feature][5] \| [Geometry][6])** Any GeoJSON Feature or Geometry - `options` **[Object][8]** Optional parameters (optional, default `{}`) - `options.featureIndex` **[number][3]** Feature Index (optional, default `0`) - `options.multiFeatureIndex` **[number][3]** Multi-Feature Index (optional, default `0`) - `options.geometryIndex` **[number][3]** Geometry Index (optional, default `0`) - `options.coordIndex` **[number][3]** Coord Index (optional, default `0`) - `options.properties` **[Object][8]** Translate Properties to output Point (optional, default `{}`) - `options.bbox` **[BBox][14]** Translate BBox to output Point (optional, default `{}`) - `options.id` **([number][3] \| [string][9])** Translate Id to output Point (optional, default `{}`) **Examples** ```javascript 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> // First Segment of the 2nd Multi-Feature turf.findPoint(multiLine, {multiFeatureIndex: 1}); // => Feature> // Last Segment of last Multi-Feature turf.findPoint(multiLine, {multiFeatureIndex: -1, coordIndex: -1}); // => Feature> ``` Returns **[Feature][5]<[Point][15]>** 2-vertex GeoJSON Feature Point [1]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function [2]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array [3]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number [4]: https://tools.ietf.org/html/rfc7946#section-3.3 [5]: https://tools.ietf.org/html/rfc7946#section-3.2 [6]: https://tools.ietf.org/html/rfc7946#section-3.1 [7]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean [8]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object [9]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String [10]: https://tools.ietf.org/html/rfc7946#section-3.1.4 [11]: https://tools.ietf.org/html/rfc7946#section-3.1.6 [12]: https://tools.ietf.org/html/rfc7946#section-3.1.5 [13]: https://tools.ietf.org/html/rfc7946#section-3.1.7 [14]: https://tools.ietf.org/html/rfc7946#section-5 [15]: https://tools.ietf.org/html/rfc7946#section-3.1.2 --- This module is part of the [Turfjs project](http://turfjs.org/), an open source module collection dedicated to geographic algorithms. It is maintained in the [Turfjs/turf](https://github.com/Turfjs/turf) repository, where you can create PRs and issues. ### Installation Install this module individually: ```sh $ npm install @turf/meta ``` Or install the Turf module that includes it as a function: ```sh $ npm install @turf/turf ```