read out KML FIle with Javascript

Question

i have a KML File with Districts of a City and want to read it out with Javascript in order to display these Overlays(Polygons) on a Map(Google Maps API v.3) Further i want to save the GeoPoints from the KML File and the Names of the Districts in an Object. But i dont know how to do that. May anyone please help me with this Problem. Thanks

Answer 1

Here is compact KML parser code. This only for google.maps Marker and Polygon.

html

<input type='file' accept=".kml,.kmz" onchange="fileChanged()">

script, I used typescript but it is pretty same with javascript

  file: any
  fileChanged(e) {
    this.file = e.target.files[0]
    this.parseDocument(this.file)
  }
  parseDocument(file) {
    let fileReader = new FileReader()
    fileReader.onload = async (e: any) => {
      let result = await this.extractGoogleCoords(e.target.result)

      //Do something with result object here
      console.log(result)

    }
    fileReader.readAsText(file)
  }

  async extractGoogleCoords(plainText) {
    let parser = new DOMParser()
    let xmlDoc = parser.parseFromString(plainText, "text/xml")
    let googlePolygons = []
    let googleMarkers = []

    if (xmlDoc.documentElement.nodeName == "kml") {

      for (const item of xmlDoc.getElementsByTagName('Placemark') as any) {
        let placeMarkName = item.getElementsByTagName('name')[0].childNodes[0].nodeValue.trim()
        let polygons = item.getElementsByTagName('Polygon')
        let markers = item.getElementsByTagName('Point')

        /** POLYGONS PARSE **/        
        for (const polygon of polygons) {
          let coords = polygon.getElementsByTagName('coordinates')[0].childNodes[0].nodeValue.trim()
          let points = coords.split(" ")

          let googlePolygonsPaths = []
          for (const point of points) {
            let coord = point.split(",")
            googlePolygonsPaths.push({ lat: +coord[1], lng: +coord[0] })
          }
          googlePolygons.push(googlePolygonsPaths)
        }

        /** MARKER PARSE **/    
        for (const marker of markers) {
          var coords = marker.getElementsByTagName('coordinates')[0].childNodes[0].nodeValue.trim()
          let coord = coords.split(",")
          googleMarkers.push({ lat: +coord[1], lng: +coord[0] })
        }
      }
    } else {
      throw "error while parsing"
    }

    return { markers: googleMarkers, polygons: googlePolygons }

  }

output

markers: Array(3)
0: {lat: 37.42390182131783, lng: -122.0914977709329}
...

polygons: Array(1)
0: Array(88)
0: {lat: -37.79825999283025, lng: 144.9165994157198}
...