Get rid of weak typing and improve your assertions: A tiny helper method for Javascript

Since checking variable types and existence always has been painful in Javascript, validation assertions normally are exhausting to write. This module solves this definitely.

• IsSet Helper
  • Browser Compatibility
  • Installation
    • as a module
    • in the browser
  • Usage
  • Contributing
  • License

Install the library through your preferred package manager:

$ npm install --save isset-helper
# or
$ yarn add isset-helper

Then you can require the module as usual:

const isset = require('isset-helper');

Include one of the following script tags in your pages head:

<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/isset.min.js"></script>
<script src="https://cdn.jsdelivr.net/gh/mcstreetguy/[email protected]/dist/isset.min.js"></script>
<script src="https://bundle.run/[email protected]/dist/isset.min.js"></script>
<script src="https://unpkg.com/[email protected]/dist/isset.min.js"></script>

The library registers the isset function automatically on the window object.

isset(variable, type);

variable can be anything, it's value is going to be checked. type can be a string, object constructor or even be omitted.

The algorithm follows the subsequent rules:

1. variable is not null
2. variable is not undefined
3. If type is a string, typeof variable has to match type, otherwise variable has to match instanceof type
4. If type is "string", the length of variable is greater than zero
5. If type is "array", variable has to pass the Array.isArray() check
6. If type is "integer", variable has to pass the Number.isInteger() check
7. If type is "float" or "double", the inverse of rule 6 applies (Number.isInteger() has to return false)

Please notice:

• The algorithm doesn't check for the exact value (apart from the empty string case mentioned above), thus false, 0 and other "falsy" values will also be considered valid.

If, contrary to expectations, you find an error in the function, please report it to the Issues page. Feel free to make changes to a fork yourself and propose a detailed pull request when finished.

This library is licensed under the MIT License. You may find a copy of the license at the root of the project source.