how to calculate the length of lineString？(ps: the result is in meters or kilometers)

[Jackyclearliu]

maptalks's version and what browser you use?

Issue description

Please provide a reproduction URL (on any jsfiddle like site)

[deyihu]

@Jackyclearliu You can use some third-party libraries to solve your needs

such as turfjs,jsts etc

const geojson=line.toGeoJSON();

const distance=turf.length(turf.linestring(geojson))