SOLID / DRY principles

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In software development, Object-Oriented Design plays a crucial role when it comes to writing flexible, scalable, maintainable, and reusable code. There are so many benefits of using OOD but every developer should also have the knowledge of the SOLID principle for good object-oriented design in programming. The SOLID principles are designed to help developers design robust, maintainable applications. The five SOLID principles are: Single-responsibility principle - Function and classes should have one job. Open–closed principle - Classes and functions should be open for  extension but not for modification. Liskov substitution principle - Child class can replace parent class Interface segregation principle - This principle is the first principle that applies to Interfaces instead of classes in SOLID and it is similar to the single responsibility principle. It states that “do not force any client to implement an interface which is irrelevant to them“. Here your main goal is ...
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Closure in Java Script

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Closures are an important concept in JavaScript that allow functions to retain access to variables from their parent scopes, even after the parent function has finished executing. Closures are created when an inner function is returned or passed as an argument to an outer function. They provide a way to encapsulate data and behavior, creating private variables and functions. Here's a real-time example that demonstrates the need for closures:

```javascript
function createCounter() {
  let count = 0;

  function increment() {
    count++;
    console.log(count);
  }

  return increment;
}

const counter = createCounter();
counter(); // Output: 1
counter(); // Output: 2
counter(); // Output: 3
```

In this example, the `createCounter` function creates a closure by defining an inner function called `increment`. The `increment` function has access to the `count` variable declared in its parent scope (`createCounter`). When `createCounter` is invoked, it initializes `count` to 0 and returns the `increment` function. The returned `increment` function forms a closure with the `count` variable, allowing it to increment and log the updated count each time it is called.

Closures are required in scenarios where you need to:
1. **Create Private Variables**: Closures provide a way to create variables that are only accessible within a specific scope, making them private and inaccessible from outside. In the example above, the `count` variable is not directly accessible from outside `createCounter`, but the `increment` function can still access and modify it.

2. **Maintain State**: Closures enable functions to retain their own state even after the parent function has finished executing. In the example, the `count` variable maintains its value across multiple invocations of the `increment` function.

3. **Create Function Factories**: Closures allow you to create and return specialized functions with predefined behavior or configurations. The `createCounter` function acts as a function factory, producing unique `increment` functions with their own separate count state.

Closures are a powerful mechanism in JavaScript that helps in creating modular and reusable code, implementing encapsulation and data privacy, and maintaining state. They provide a way to create functions that "remember" and can access variables from their lexical environment, even when executed in a different scope or context.

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