One rule to validate several inputs with Backbone.validation

Question

I have 10 inputs for instance. And I want to check if they're empty using one rule but avoiding reiteration like this:

firstInput :{
    required: true,
    msg: 'Empty!'
},
// ...

tenthInput :{
    required: true,
    msg: 'Empty!'
}

Is there any method to use one rule for all inputs using Backbone Validation? And each input can have other unique validation rules the same time, e.g.:

firstInput :{
    pattern: email,
    msg: 'Email!!!'
}

Answer 1

From the Backbone Validation documentation:

// validation attribute can also be defined as a function returning a hash
var SomeModel = Backbone.Model.extend({
  validation: function() {
    return {
      name: {
        required: true
      }
    }
  }
});

You could then adjust your model to have a function:

var SomeModel = Backbone.Model.extend({
    /**
     * List of field which are required.
     * @type {Array|Function}
     */
    required: ['firstInput', 'secondInput', /*...*/ 'tenthInput'],
    /**
     * Same format as Backbone Validation
     * @type {Object|Function}
     */
    specificValidation: {
        firstInput: {
            pattern: "email",
            msg: 'Email!!!'
        }
    },

    validation: function() {
        var inputs = _.result(this, 'required'),
            rules = _.result(this, 'specificValidation'),
            requiredRule = { required: true, msg: 'Empty!' };

        // apply the default validation to each listed field
        // only if not already defined.
        _.each(inputs, function(field) {
            rules[field] = _.defaults({}, rules[field], requiredRule);
        });

        return rules;
    }
});