choan/js_attributes

A one-object-library to isolate JavaScript attributes – includes validation and basic observers

Attributes

Attributes is a one-object-library, created as an experiment to isolate JavaScript object attributes.

Features:

• Undeclared attributes are not allowed to be set
• Validation
• onchange callbacks
• Bypassing the set and get methods is not possible
• Inclusion on host objects

Usage

Create an Attributes instance:

var conf = new Attributes();

Declare acceptable attributes with the chainable add method:

conf.add('name').add('surname');

You can set validations and onchange callbacks on attributes (check Attributes.validations for allowed methods. Add more methods as needed):

conf.add('age', [ ['numeric'], ['min', 18] ]);

The callback function is called with three arguments: the name of the attribute, the new value and the old value. Context of invocation is not modified. Value is not changed if the callback returns false.

conf.add('name', null, function(name, newValue, oldValue) {
  console.log(name, 'changed from', oldValue, 'to', newValue);
});

Setting and getting attributes:

// returns true if the attribute value
// is set, otherwise returns false
conf.set('name', 'Choan');

// returns the value of the attribute
// or undefined if not set
conf.get('surname');

You can merge objects-as-hashes on the collection of values:

conf.merge({
  name: 'Choan',
  surname : 'Galvez',
  age: 32
});

Use the each method to iterate. The callback is invoked with value and key as arguments. Context is not modified.

conf.each(function(v, k) {
  console.log(k, 'is', v);
});

Including in other objects

Use the Attributes.on to merge an Attributes instance on host objects. Methods are renamed in the following form:

• add, set, get and each are addAttribute, setAttribute, etc.
• merge is mergeAttributes

An example:

var Client = function() {
  Attributes.on(this);
  this
    .addAttribute('name')
    .addAttribute('surname')
    .addAttribute('age', [ ['numeric'], ['min', 18] ]);
};

var client = new Client();
client.setAttribute('name', 'Choan');
client.setAttribute('surname', 'Gálvez');
client.setAttribute('age', 32);
client.eachAttribute(function(value, key) {
  console.log(key, 'is', value);
});

Check the source and the tests for more info.

License

Attributes has been created by Choan Galvez and is freely distributable under the terms of a MIT-style license. The source code resides in a Git repository at github.