isset-helper

Isset Helper

A tiny helper method for Javascript, checking a variable for existence.

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

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Installation

as a module

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');

in the browser

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

<script src="https://cdn.jsdelivr.net/npm/isset-helper@2/dist/isset.min.js"></script>
<script src="https://cdn.jsdelivr.net/gh/mcstreetguy/isset-helper@2/dist/isset.min.js"></script>
<script src="https://bundle.run/isset-helper@2.0/dist/isset.min.js"></script>
<script src="https://unpkg.com/isset-helper@2/dist/isset.min.js"></script>

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

Usage

isset(variable, type);

variable can be anything. It's value is going to be checked.
type can be a string, class or even left out.

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
4. Otherwise, variable has to match instanceof type
5. If type is "string", variable is not an empty string

Please notice:

• The algorithm always runs the instanceof-check, leaving it out of consideration if the check produces any error.
• The algorithm doesn't check for the exact value (apart from the empty string case mentioned above), thus false will also be considered valid.

Contributing

If, contrary to expectations, you find an error in the function, please report it to the Issues page.

License

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