Unveiling the Magic of is.undefined and is.not_undefined with 'thiis': Navigating the Undefined Realms in JavaScript
Tags: coding, codenewbie, programming, beginners
Published: 2023-11-22 11:33:48

JavaScript is a realm of endless possibilities, and one of its intriguing mysteries lies in the concept of `undefined`. Handling situations where values are undefined is a common challenge for developers. Fear not, for the `is.undefined` and `is.not_undefined` methods from the 'thiis' package are here to guide you through the undefined realms of JavaScript. In this article, let's embark on an adventure to unravel the magic of these tools with fun and practical examples.

## The Enigmatic World of `undefined` in JavaScript


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/r8ctppx85sn3zsxut2e1.jpeg)

Before we dive into our exploration, let's demystify what `undefined` means in JavaScript. It signifies the absence of a value or the lack of an assigned value to a variable. Recognizing and handling `undefined` is crucial for writing robust and bug-free code.

## Meet `is.undefined` - Your Undefined Navigator

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

Imagine you're on a quest to navigate the undefined territories in your code. The `is.undefined` method acts as your seasoned navigator, ensuring that a value is indeed `undefined`. Let's witness its magic:

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

let myUndefinedValue;
const result = is.undefined(myUndefinedValue);

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

In this example, we import the "is" object from the "thiis" package and use the `is.undefined` method to confirm that `myUndefinedValue` is indeed `undefined`. As expected, it returns `true` because the value is, in fact, `undefined`.

## The Expedition of Examples

Now, let's embark on an exciting journey through a variety of examples that showcase the versatility of `is.undefined` and its trusty companion, `is.not_undefined`.

### 1. **Detecting Undefined Values**

The primary role of `is.undefined` is to identify when a value is `undefined`. It comes in handy when dealing with situations where a variable might not be assigned a value:

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

let potentialUndefined;
if (is.undefined(potentialUndefined)) {
  // Handle the situation gracefully.
} else {
  // Continue with confidence.
}
```

### 2. **Guarding Against Undefined Values**

Conversely, `is.not_undefined` is your guardian against `undefined` values. It ensures that a value is not `undefined` before proceeding with operations:

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

const importantValue = someFunctionThatShouldNotReturnUndefined();

if (is.not_undefined(importantValue)) {
  // Proceed with confidence.
} else {
  // Handle undefined scenarios.
}
```

### 3. **Validating Function Parameters**

When defining functions, it's essential to validate parameters to avoid unexpected `undefined` values:

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

function greetUser(name) {
  if (is.undefined(name)) {
    return 'Hello, mysterious stranger!';
  } else {
    return `Hello, ${name}!`;
  }
}
```

### 4. **Ensuring Object Properties Exist**

When working with objects, ensure that a property exists before trying to access it:

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

const user = {
  name: 'John',
  age: 25,
  // No address property
};

if (is.not_undefined(user.address)) {
  // Safely access and use the address property.
} else {
  // Handle the absence of the address property.
}
```

### 5. **Navigating Streams with `is.undefined`**

Let's explore a scenario involving `stream$` from RxJS. Using `filter` and `is.undefined`, we can ensure that the stream processes only values that are `undefined`:

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

const stream$ = from([undefined, 'not undefined', null, 0, 'a value']);

stream$
  .pipe(
    filter(is.undefined)
  )
  .subscribe(value => {
    console.log(value); // Only undefined values will be part of the stream's story.
  });
```

In this example, the `filter(is.undefined)` ensures that only `undefined` values get processed by the stream.

### 6. **Array Exploration with `is.not_undefined`**

Arrays offer another playground for `is.not_undefined`. You can use `every()` to confirm that all elements are not `undefined` and `some()` to check if at least one isn't:

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

const notUndefinedArray = [1, 'not undefined', true];
const mixedArray = [undefined, 'not undefined', null, undefined];

const allElementsNotUndefined = notUndefinedArray.every(is.not_undefined); // true
const someElementsNotUndefined = mixedArray.some(is.not_undefined); // true

console.log(allElementsNotUndefined);
console.log(someElementsNotUndefined);
```

Here, `allElementsNotUndefined` checks if all elements in `notUndefinedArray` are not `undefined`, and `someElementsNotUndefined` checks if at least one element in `mixedArray` is not `undefined`.

## The Adventure Continues

The `is.undefined` and `is.not_undefined` methods from the 'thiis' package are your reliable guides through the undefined realms of JavaScript. They make handling `undefined` values playful and precise, ensuring your code navigates the undefined territories with confidence. By adding the 'thiis' package to your JavaScript toolkit and exploring its documentation for more tips and examples, you can boldly venture into the unknowns of JavaScript coding.

So, keep coding, and remember that the undefined realms are full of surprises! 

> 🎗 ChatGPT & DALL·E 3