Date attributes on model - backbone.js

Question

Is there any way to get ISO-dates parsed as javascript-dates om Backbone models.
Let's say some JSON returns model data like this:
{ prop1: "somevalue", date: "2011-05-11T18:30:00" }
To make this work as a date, i came up with this:
var Model = exports.Model = Backbone.Model.extend({
toJSON: function () {
return _.extend(this.attributes, {
date: new Date(this.attributes.date)
});
}
});
This works fine, and makes it possible to write template-markup as this:
"<%=date.toLocaleDateString() %>"
Its all fine, but couldn't it be done at the BackboneModel prototype somehow. This way i have to write this implementation, on every model property of type date - thats not very DRY

Answer 1

Because the JSON ISO8601-formatted dates are just strings, there is no magical way of just parsing them. You need to either declare or detect the fields which should be parsed.
Declaration is easy, just define an array of date fields on the model an parse each of them.
//declare dateFields on the model
var TestModel = Backbone.Model.extend({
dateFields: [
'createdDate',
'updatedDate'
]
});
//override toJSON
Backbone.Model.prototype.toJSON = function() {
return this._parseDates(this.attributes);
};
//hydrates string dates to Date objects
Backbone.Model.prototype._parseDates = function(attrs) {
attrs = _.clone(attrs);
if(!this.dateFields) { return attrs; }
_.each(this.dateFieds, function(field) {
attrs[field] = new Date(attrs[field]);
});
return atts;
};
That requires you to tell the date parser which fields to consider. Since you were hoping for something more automagical, the other option is to try to detect which fields are dates by looking at the shape of each string value:
//hydrates string dates to Date objects
Backbone.Model.prototype._parseDates = function(attrs) {
attrs = _.clone(attrs);
var iso8601Pattern = /^[0-9][0-9][0-9][0-9](-[0-1][0-9](-[0-3][0-9](T[0-9][0-9](:[0-9][0-9](:[0-9][0-9])(\.[0-9][0-9][0-9]?)?)?)?)?)?Z$/;
_.each(attrs, function(value, key) {
if(_.isString(value) && iso8601pattern.test(value)) {
attrs[key] = new Date(value);
}
});
return attrs;
};
Which doesn't require you to list all the date fields, but will add overhead to parsing, because it needs to test each value to see if it looks like a date.