ensurethat

ensurethat

ensurethat makes handling arguments a breeze.

Installation

$ npm install ensurethat

Quick start

First you need to add a reference to ensurethat to your application.

var ensure = require('ensurethat');

Now you are able to use the that function to describe the function's arguments using validators. Currently, the following built-in validators are provided.

• ensure.boolean(), aliased as 'boolean', default value is false
• ensure.function(), aliased as 'function', default value is a no-op function
• ensure.number(), aliased as 'number', default value is 0
• ensure.object(), aliased as 'object', default value is null
• ensure.string(), aliased as 'string', default value is ''
• ensure.uuid(), aliased as 'uuid', default value is '00000000-0000-4000-89ab-000000000000'

var add = function () {
  var args = ensure.that(arguments).are({
    first: ensure.number(),
    second: ensure.number()
  });

  return args.first + args.second;
};

Basically all validators are functions, but those that do not need configuration come with alias names, so that you can also use them by their name.

var add = function () {
  var args = ensure.that(arguments).are({
    first: 'number',
    second: 'number'
  });

  return args.first + args.second;
};

Anyway, if everything is fine, the that function returns an object which contains a property for each argument. Otherwise, it throws an error with an appropriate error message.

As the arguments are accessed using the arguments and args variables, you may skip specifying the arguments within the function's signature completely, as shown in the samples above. This also makes sure that you do not get linting errors such as no-unused-vars.

Handling optional arguments

If you want to mark an argument as optional, surround its validators with brackets.

var args = ensure.that(arguments).are({
  first: 'number',
  second: [ 'number' ]
});

For each validator there is a default value which is used to initialize optional arguments. If you want to override this default value you can specify a default value manually.

var args = ensure.that(arguments).are({
  first: 'number',
  second: [ 'number', 23 ]
});

You can also have multiple optional arguments, but within a specific type optional arguments must always come last. Hence, the following sample is fine.

var args = ensure.that(arguments).are({
  first: 'number',
  second: [ 'number', 23 ],
  third: [ 'number', 42 ],
  fourth: 'string'
});

Using custom validators

From time to time there are special requirements for validating arguments. For that you can create a custom validator by providing a function that returns an empty constructor function with a name property as well as an isValid and a defaultValue function attached to its prototype.

var customValidator = function () {
  var Validator = function () {};

  Validator.prototype.name = '...';

  Validator.prototype.isValid = function (value) {
    // ...
    // Return true or false, depending on whether the value is valid.
  };

  Validator.prototype.defaultValue = function () {
    // ...
    // Return the default value in case this validator is being used
    // for a missing optional argument without an explicitly given
    // default value.
  };

  return Validator;
};

Now you can use this custom validator by calling it instead of a built-in one when calling that.

var args = ensure.that(arguments).are({
  first: ensure.number(),
  second: customValidator()
});

Creating configurable validators

If you want to create a configurable custom validator, add arguments to the validator setup function, and provide them when using the validator.

var range = function (min, max) {
  var Validator = function () {};

  Validator.prototype.name = 'range';

  Validator.prototype.isValid = function (value) {
    return min <= value && value <= max;
  };

  Validator.prototype.defaultValue = function () {
    return min;
  };

  return Validator;
};

var args = ensure.that(arguments).are({
  first: ensure.range(23, 42)
});

Running the build

This module can be built using Grunt. Besides running the tests, this also analyses the code. To run Grunt, go to the folder where you have installed ensurethat and run grunt. You need to have grunt-cli installed.

$ grunt

License

The MIT License (MIT) Copyright (c) 2013-2014 the native web.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.