propReduce

描述

¥Description

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.

参数

¥Parameters

名称	类型	描述
geojson	FeatureCollection | 特性 | 几何图形	任意 GeoJSON 对象
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.

返回

¥Returns

Reducer The value that results from the reduction.

示例

¥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;
  },
);

安装

¥Installation

$ npm install @turf/meta

import { propReduce } from "@turf/meta";
const result = propReduce(...);

$ npm install @turf/turf

import * as turf from "@turf/turf";
const result = turf.propReduce(...);