Can I force an update to a model's attribute to register as a change even if it isn't?

Question

I know that I can set the value of a Backbone model's attribute so that it doesn't trigger a change event using {silent:true}. I also know that if I set a model's attribute to a value it already has, it won't trigger a change event, which is almost always a good thing. However, is there a way to force the update to the model to trigger a change event even if it's set to the same value?

So if within my model I have set:

defaults:{
    attributeToChange: "myValue"
}

And then in the a view using this model I call:

this.model.set('attributeToChange', 'myNewValue', {silent:true});

the value will change but no change event will be fired. But what if I wanted to have a change event fired whenever the attribute's value was set, regardless of what it was set to? So if instead I just did

this.model.set('attributeToChange','myValue');

is there a parameter I can add that will force this to be seen as a change? I believe that I can use

this.model.trigger('change:attributeToChange');

but I'd like to know if there's a way to force the change event to fire without this.

Bonus question: If I set a model's attribute to a value it already has, does this make the attribute's previous value the value it had before I initiated the change?

this.model.set('attributeToChange','someValue');
this.model.set('attributeToChange','anotherValue');
this.model.set('attributeToChange','anotherValue');
console.log(this.model.previous('attributeToChange')); //someValue or anotherValue?

Answer 1

When you set a value to a model in Backbone, Backbone will compare the new value to the current ones, and add the changed values to an array (see https://github.com/documentcloud/backbone/blob/master/backbone.js#L342).

Then, if the changes array contains element, Backbone will triggers the "change:{key}" event for each changed item if silent is not set to true. (see https://github.com/documentcloud/backbone/blob/master/backbone.js#L357).

Finally, it will also trigger the global "change" event (again, if silent is not set to true).

So if you want to force the trigger on non-changed attributes, you can manually trigger the event, like Backbone does, or override the set method like @Loamhoof suggested.