Removes all items from the collection.  Fires the {@link #event-clear} event when complete.
@since Ext 1
function() {
        var me = this;

        me.length = 0;
        me.items = [];
        me.keys = [];
        me.map = {};
        me.indexMap = {};

        me.generation++;
        me.indexGeneration = me.generation;
        if (me.hasListeners.clear) {
            me.fireEvent('clear');
        }
    }