Sorting the feature list

So far, no use has been made of the third piece of data in the coordinates list, which is the depth of the quake. This data will be presented in the form of a sorted list of the current features when the user presses the Sort button. Let's have a look at the following code snippet:

void sortFeatures(Event evt) {
  featPlotter.sortFeatures();
  DivElement out = querySelector('#depthDetail');
  out.nodes.clear();
  featPlotter.geoFeatures.forEach((feature) {
    LIElement detail = new LIElement();
    detail.innerHtml = "${feature[5]}km - ${feature[3]}";
    out.nodes.add(detail);
  });
}

The list of features is sorted in the method sortFeatures, and as Dart knows nothing of the meaning of the contents of the list, we provide a comparator function that decides which feature is deeper by comparing the depth measurement held at index 5 of the list:

  List sortFeatures(){
    geoFeatures.sort( (a,b) => a[5] - b[5] );
    return geoFeatures;
  }

The comparator receives two arguments and returns 0 for items that are equal, a negative integer if a is less than b, or a positive integer if a is greater than b. Let's have a look at the following screenshot:

The depths are sorted in ascending order and presented as a simple bulleted list together with the location information.