Essential GeoJSON scripts part CXLVIII

Use this little class to iterate over the features of a GeoJSON object and do stuff with them. Has a .forward() and a .rewind() method, just like the good old cassette recorder. Use it with e.g. events to iterate programmatically through the features in an endless loop.

Create the GeoJsonScroller as follows: var scroller = new GeoJsonScroller(geoJsonDataObject, getDataFunction, sortFunction);

You can use notable methods on the class:

• getData(): retrieves the data for the current feature
• forward(): move on to the next feature and get its data. If the end is reached, continue from start
• rewind(): go back one feature and get its data. If the start is reached, continue with the last feature in the feature's array

You need to pass a function to retrieve data from a feature:

function getData (feature) {
  var data = {},
      cols = [ "title", "desc", "image", "icon", "color", "category",
               "pitch", "bearing", "zoom", "speed", "curve" ];
  data["center"] = feature.geometry.coordinates;

  for (var key in feature.properties) {
    if (cols.indexOf(key) > -1) { data[key] = feature.properties[key]; }
  }
  return data
}

scroller = new GeoJsonScroller(myGeoJson, getData);
var data = scroller.forward();

You can pass a function in order to sort the features by some criteria. Have a look at the docs for how to write such a function.

// this works for numerical props
function sortById (a, b) {
  return a.properties.id - b.properties.id;
}

function getData (feature) {
  // bla
}

scroller = new GeoJsonScroller(myGeoJson, getData, sortById);
var data = scroller.forward();

Have fun!