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A simple, convenient and ECMAScript 3 compliant protocol testing API for JavaScript.
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Protocol Kit is a simple, convenient and EcmaScript 3 compliant protocol testing API for JavaScript.

Supports Nodejs, Bower, AMD and loading as a global browser <script>.


bower install protocol-kit


npm install protocol-kit


To use the component you will have to bundle the component using a tool like Browserify. For example:


var proto = require('protocol-kit')
console.log(typeof proto)

command line:

browserify -t debowerify ./public/modules/app.js > ./public/app.max.js

Example usage

Create a simple protocol for a user.

var userProtocol = protocolKit({name: 'string', age: 'int'});
var user = {name: 'Darren, age: 31};

if (userProtocol.describes(person)) {
  // do stuff with person
} else {
  // throw error

Create a protocol that describes a group that must have a homogenous array of users.

var groupProtocol = protocolKit({users: [userProtocol]});
var group = {users: []};
groupProtocol.describes(group); // true
group.users.push({name: 'Darren', age: 31});
group.users.push({name: 'Alex', age: 33});
groupProtocol.describes(group); // true

If the users contains an element that is not a user then it will fail the protocol test.

group.users.push('Dave, 35');
groupProtocol.describes(group); // false

Let's update our "user" protocol so that each user can have a non-sparse, heterogenous array of "stuff".

userProtocol.descriptor().stuff = ['*'];

Now each user must have at least an array of stuff, but it can be empty.

groupProtocol.describes(group); // false
group.users[0].stuff = [1, 2, '3'];
group.users[1].stuff = new Array(10); // sparse array sized to 10 elements
groupProtocol.describes(group); // false 

User at index 1 has an array of stuff, but it's sparse. We must set it to an empty array instead.

group.users[1].stuff = [];
groupProtocol.describes(group); // true

Let's add a timestamp to each group.

group.timestamp = new Date();
groupProtocol.describes(group); // true

Since the timestamp is not in the protocol the protocol still describes the group. But we can make the protocol include the timestamp.

groupProtocol.descriptor().timestamp = Date;
groupProtocol.describes(group); // true

Lastly, let's add an optional list of tags to each user using the '@optional' custom rule.

userProtocol.descriptor()['@optional'] = {tags: ['string']};
group.users[0].tags = ['male', 'computer science'];
groupProtocol.descriptor(group); // true

The group protocol still describes the group because user tags are optional, but when the tags array does exist it must be a homogenous array of strings.

group.usrs[1].tags = [1, 'slacker'];
groupProtocol.describes(group); // false


protocolKit.registerRule(name, handler)


Protocols From Existing Objects

Sometimes you will have an existing code base you may want to start using protocols for, or you want a fast way to create a protocol from an existing object. Protocol-Kit can create protocols from objects by calling protocolKit.from().

var use = {name: 'Darren', age: 32};
var useProtocol = protocolKit.from(user);
var descriptor = userProtocol.descriptor();
// descriptor will be: {name: 'string', age: 'number'}


When creating a protocol you must describe the protocol using a protocol descriptor object. This object has all the rules you would like an object to have in order to adhere to the protocol.

Each rule in a protocol descriptor may can describe a property or a custom descriptor rule. All custom descriptor rules must start with '@', all other descriptor rules are property rules. Property rules can be one of the following values:

'null' = This property must be null
'string' = This property must either be a string literal or a String object
'number' = This property must either be a number literal or a Number object
'int' = This property must either be an integer literal or an integer Number object
'boolean' = This property must either be a boolean literal or a Boolean object
'function' = This property must be a function
'array' = This property must be a homogenous or heterogenous and/or sparse array with any number of elements
'object' = This property must be an object with a prototype (literals will fail)
'*' = This property must be non-null and defined
constructor function = This property must be an instance of the specified constructor
[any supported type] = This property must be a homogenous array whos' elements must be the type specified by the first element
another protocol = This property must pass the describes() test of another protocol

Custom Rules

Custom rules are rules that start with '@' and opperate on a group of property rules. The following custom rules are supported by default:

'@optional' - This rule passes if all property rules that can be applied pass. Only if the property exists will a rule apply.
'@either-or' - This rule passes only if one and only one of its property rules passes.


// Optional properties
  name: 'string',
  '@optional': { 
    age: 'int', 
    gender: 'string' 

// Either-or (i.e. one-of from a set of properties)
  name: 'string',
  '@either-or': {
    male: 'boolean',
    female: 'boolean'

Registering Custom Rules

To register custom rules you would call protocolKit.registerRule() with your rule name (without the leading '@' character) and rule handler. The rule handler must accept the following arguments:

  • descriptor = The descriptor that is the value of the custom rule.
  • instance = The instance being tested.
  • testPropertyRule = The function used to test each property rule in the descriptor.

The testPropertyRule function has the following signature:

testPropertyRule(ruleName, descriptor, instance)

This function will return true or false depending if the property rule pases.

NOTE: Although it is the intention that descriptor be an object with property rules, this value can be anything that the custom rule accepts.

The custom rule handler function must return true if the rule passes and false otherwise.

protocolKit.registerRule() will not register rules with the same name and will return false if an attempt is made to do so or if the arguments are not of the expected type. This function returns true otherwise.

Custom Property Rules

Cusotm property rules are rules that apply to individual properties. The following built-in custom property rules are supported:

  • enumerations Format: "enum{value1,value2,value3}" or ["enum{", value1, value2, value3, "}"] Example: {type: 'enum{circle,triangle,rectangle}'}

Registering Custom Property Rules

You can register custom property rules by calling protocolKit.registerPropertyRule() with the a rule object. A rule object must have the following methods:

  • match(rule) = The method called to test a rule for a match.
  • test(rule, value) = The method called to test a rule for validity (match must return true before test is called).


// Add a custom property rule to support hex color strings.
  match: function (rule) { return rule === 'hexstring'; },
  test: function (rule, value) {
    return typeof value === 'string' && value.charAt(0) === '#' && parseInt(value.substr(1), 16) >= 0;

// Usage
  type: 'enum{circle,triangle,rectangle}',
  cssColor: 'hexstring'
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