You're passing the raw array of your models to your template and a model is not a hash, you don't have direct access to the properties.
Either use collection.toJSON
self.template({ articles: self.collection.toJSON() })
or use model.get
in your template
<%= a.get('title') %>
Note that in your example JSON.stringify
will give you the expected representation of your data because
toJSON behavior
If an object being stringified has a property named toJSON whose value is a function, then the toJSON method customizes JSON stringification behavior: instead of the object being serialized, the value returned by the toJSON method when called will be serialized.
and your models have a toJSON
method.