Easiest way to reset Backbone's model to initial defaults?

myModel.clear().set(myModel.defaults);

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I came up with the following approach:

reset: function () {
    this.clear({silent: true});
    this.set(this.defaults);
}

Having {silent: true} in the clear() call ensures that the change event is not fired; it will be fire only on set() call.

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I do this when the model has non-null initial object properties.

first, define defaults as a function

var MyModel = Backbone.Model.extends({

    defaults:function(){

        return {
            AnArrayTypeProp:[]
        };
    }

});

second, when needed to reset model to default

model.clear().set(model.defaults());

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Based on saabeilin's answer and Backbone's annotated source, I came with an optimal function to fill the need for resetting a model.

Reusable reset

/**
 * Clears the model's attributes and sets the default attributes.
 * @param  {Object} attrs to overwrite defaults
 * @param  {Object} options  to pass with the "set" call.
 * @return {Backbone.Model}  this object, to chain function calls.
 */
reset: function(attrs, options) {
    // adds default option reset to true
    options = _.extend({ reset: true }, options);

    // ensure default params
    var defaults = _.result(this, 'defaults');
    attrs = _.defaults(_.extend({}, defaults, attrs), defaults);

    // apply
    this.clear({ silent: true }).set(attrs, options);

    // triggers a custom event, namespaced to model in order
    // to avoid collision with collection's native reset event
    // when listening to a collection.
    if (!options.silent) this.trigger('model:reset', this, options);

    return this;
},

The following line ensures that even if an attribute is passed as undefined { test: undefined }, it'll still have its default value.

attrs = _.defaults(_.extend({}, defaults, attrs), defaults);

Here's an example:

var defaults = { test: 1 }, 
    attrs = { test: undefined };

_.extend({}, defaults, attrs);                       // {test: undefined}
_.defaults(_.extend({}, defaults, attrs), defaults); // {test: 1}

Extending Backbone

And if you want it with all Backbone models, you can extend Backbone itself:

_.extend(Backbone.Model.prototype, {
    reset: function(attributes, options){
        /* ... */
    }
});

Disclaimer: Don't do this if you're writing a JavaScript lib or Backbone plugin, as it could collide with another lib or it could cause a different behavior than the one expected by the person using your code.

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I also thought about using model.clear() and model.set() in conjunction. Then I ran across the problem, that I trigger the change event twice now. Using the silent option when calling model.clear() is not an option, because I also want to have a change event fired, when a property gets unset.

I ended up with adding a model.reset() method. It takes a new attributes hash and fills this hash with undefined values for old attributes keys not being present in the new attribute hash.

Model.prototype.reset = function(attrs, options) {
    for (var key in this.attributes) {
        if (key in attrs) continue;
        attrs[key] = void 0;
    }

    return this.set(attrs, options);
};

This way you reset the models old attributes and get a valid change event for every old and new attribute.

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What about overriding the value of current model with a new empty model :

myModel = new model(); // default values will be considered

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My solutions is:

model.clear({silent: true}).set(model.defaults);

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