How to properly reverse sort a BackboneJs collection? - sorting

Question

I have a table where several items are displayed.
<table>
...
<th scope="col">Priority <a id="sort"><i class="fas fa-chevron-down"></i></a> <a id="sort2">
<i class="fas fa-chevron-up"></i></a></th>
...
</table>
The priorities holds an integer value, 1, 2 and 3 respectively.
I'm trying to sort the items on button click. I managed to sort once by using collection.sort() in my view and it sorts perfectly. How can i reverse sort by clicking sort2 button? Any help regarding this is appreciated. Thank you.
app.views.ShareView = Backbone.View.extend({
el: ".page",
initialize: function () {},
events:{
"click #sort" : "sort",
"click #sort2" : "sort2"
},
sort: function (e){
e.preventDefault();
this.collection.comparator = 'priority_id';
this.collection.sort();
this.render();
},
sort2: function (e){
//reverse sort
}
render: function () {
template = _.template($('#share-template').html());
this.$el.html(template(app.userShare.attributes));
}
});

Answer 1

You need to use the sort comparator function instead of the comparator property. This allows you to specify a comparator function instead of just the property. For example;
this.collection.comparator = function(firstModel, secondModel) {
if(firstModel.priority_id > secondModel.priority_id) { // change to < in order reverse the order
return -1;
}
else if(firstModel.priority_id === secondModel.priority_id) {
return 0;
}
else {
return 1;
}
}
this.collection.sort();
In BackboneJS, it is often possible to use a function in place of a value if you require additional functionality.