BackboneJS

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Extending model classes

This example sub-classes an existing model and ensures that new instances have their type property set.

var subModel = mainModel.extend({
	constructor: function( attributes, options ) {
		attributes.type = 'subModel';
		Backbone.Model.apply( this, arguments );
	},
});

Collections of various sub-classes

Normally a collection's members are all of the same class, but you may want the members to be of various sub-classes as well. You can replace the object on the add event as follows.

myCollection.on( 'add', upgradeObject, lg );

function upgradeObject( obj ) {
	var upg = createObject( obj.attributes );
	for( var i in upg ) obj[i] = upg[i];
}

function createObject( atts ) {
	var cls = ... // figure out the sub-class you want from the atts
	var obj = new lg[cls](atts);
	for( var i in atts ) obj[i] = atts[i];
	obj.id = atts.id;
	return obj;
};

See also

• JavaScript
• UnderscoreJS