Describes the grouping of items using a property name as the criterion.

For example, the code below causes a CollectionView to group items by the value of their 'country' property:

var cv = new wijmo.collections.CollectionView(items);
var gd = new wijmo.collections.PropertyGroupDescription('country');
cv.groupDescriptions.push(gd);

You may also specify a callback function that generates the group name. For example, the code below causes a CollectionView to group items by the first letter of the value of their 'country' property:

var cv = new wijmo.collections.CollectionView(items);
var gd = new wijmo.collections.PropertyGroupDescription('country', 
  function(item, propName) {
    return item[propName][0]; // return country's initial
});
cv.groupDescriptions.push(gd);