线段累加(segmentReduce)

> npm install @turf/meta

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.

接收任意类型的 GeoJSON，遍历它的 2-vertex 线段并累加操作。功能类似 Array.reduce()。(Multi)Point几何图形不包含线段，因此在此操作期间将忽略它们。

参数

参数	类型	描述
geojson	FeatureCollection|Feature|Geometry	任意 GeoJSON 对象
callback	Function	回调，参数依次是 previousValue、currentProperties、featureIndex
initialValue	(*)	初始值

返回

undefined - undefined

示例

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);