Unveiling the Magic of is.function and is.not_function in JavaScript with 'thiis'
Tags: webdev, beginners, codenewbie, coding
Published: 2023-11-20 08:36:05

JavaScript is a realm of wonders, and at its heart lies the powerful concept of functions. They are the building blocks of dynamic and expressive code. But how can you be sure if something is truly a function or, on the flip side, anything but a function? Enter the enchanting world of `is.function` and `is.not_function` methods from the 'thiis' package. In this article, we'll embark on a delightful journey to explore these tools, unraveling their magic in the world of JavaScript.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/pd1yg7h95lu3s3q2xtgp.jpeg)

## The Spell of Functions in JavaScript

Before we set off on our magical adventure, let's take a moment to appreciate the role of functions in JavaScript. They're like spells you cast to make things happen, encapsulating logic and enabling code to perform actions.

## Meet `is.function` - Your Wizard of Functions

[Documentation link](https://karbashevskyi.github.io/thiis/docs/API/Common/is.function)

Imagine you're on a quest to distinguish between mere mortals and the magical wizards (functions) in your code. The `is.function` method is your trusty wizard detector, ensuring that a value is indeed a function. Let's see it in action:

```javascript
import { is } from 'thiis'; // Import the "is" object from the "thiis" package

const myFunction = () => {
  // A magical function indeed!
};

const result = is.function(myFunction);

console.log(result); // true
```

In this example, we import the "is" object from the "thiis" package and use the `is.function` method to confirm that `myFunction` is indeed a magical function. As expected, it returns `true` because the value is indeed a function.

## The Journey of Examples

Now, let's explore a series of whimsical examples that showcase the versatility of `is.function` and its playful companion, `is.not_function`. We'll embark on six unique scenarios, including a couple of magical ones.

### 1. **Casting Spells with `is.function`**

The primary role of `is.function` is to identify magical functions. It helps you ensure that a value is indeed a function before casting any spells:

```javascript
import { is } from 'thiis';

const spell = someMagicalFunction();

if (is.function(spell)) {
  // Cast your spell with confidence!
  spell();
} else {
  // Handle the absence of magic gracefully.
}
```

### 2. **Guarding Against Muggles with `is.not_function`**

Conversely, `is.not_function` serves as your guardian against non-magical beings (non-functions). It's handy when you want to ensure that a value isn't a function before proceeding:

```javascript
import { is } from 'thiis';

const mundaneCreature = someNonMagicalBeing();

if (is.not_function(mundaneCreature)) {
  // Guard against non-magical mishaps!
} else {
  // Time to explore magical possibilities.
}
```

### 3. **Magical Validation with `is.function`**

When working with user input, ensuring that the input is a magical function is crucial. Use `is.function` to validate and handle situations where the input might be a magical spell:

```javascript
import { is } from 'thiis';

function validateMagicalSpell(spell) {
  if (is.function(spell)) {
    // Your spell is validated and ready to cast!
    spell();
  } else {
    return 'Please provide a valid magical spell.';
  }
}
```

### 4. **Magical Conditions with `is.not_function`**

In decision-making scenarios, you might want to ensure that a value is anything but a magical function before proceeding:

```javascript
import { is } from 'thiis';

const ordinaryObject = getOrdinaryObject();

if (is.not_function(ordinaryObject)) {
  // Execute actions for non-magical scenarios.
} else {
  // Handle magical beings with grace.
}
```

### 5. **Stream of Magic with `is.function`**

Now, let's weave a magical scenario involving `stream$` from RxJS. Using `filter` and `is.function`, we can ensure that the stream processes only magical functions:

```javascript
import { is } from 'thiis';
import { from } from 'rxjs';
import { filter } from 'rxjs/operators';

const stream$ = from([() => 'A magical function', 'Not a function', () => 'Another spell', 42]);

stream$
  .pipe(
    filter(is.function)
  )
  .subscribe(spell => {
    console.log(spell()); // Only magical functions will be part of the stream's tale.
  });
```

In this example, the `filter(is.function)` ensures that only magical functions get processed by the stream.

### 6. **Array Enchantment with `is.not_function`**

Arrays are another realm where `is.not_function` can work its enchantment. Use `every()` to confirm that all elements are not magical functions and `some()` to check if at least one isn't:

```javascript
import { is } from 'thiis';

const notMagicalArray = [42, 'Not a spell', true];
const mixedArray = [() => 'A magical function', 'Just a string', null, undefined];

const allElementsNotFunction = notMagicalArray.every(is.not_function); // true
const someElementsNotFunction = mixedArray.some(is.not_function); // true

console.log(allElementsNotFunction);
console.log(someElementsNotFunction);
```

Here, `allElementsNotFunction` checks if all elements in `notMagicalArray` are not magical functions, and `someElementsNotFunction` checks if at least one element in `mixedArray` is not a magical function.

## The Adventure Continues

The `is.function` and `is.not_function` methods from the 'thiis' package are your delightful companions on your magical JavaScript adventure. They make type checking playful and precise, ensuring your code interacts with magical functions exactly as intended. By adding the 'thiis' package to your JavaScript toolkit and exploring its documentation for more tips and examples, you can navigate the JavaScript landscape with confidence and a

 sprinkle of magic.

So, wave your wand, cast your spells, and remember that the magic of JavaScript is always at your fingertips!

> 🎗 ChatGPT & DALL·E 3