[How to] write abstract functions in JS
Tags: javascript, beginners, programming, tutorial
Published: 2022-12-10 09:24:48

Abstract functions can also be useful when you want to write code that is more modular and easy to maintain. By separating the abstract concept or behavior of a function from the specific details of its implementation, you can make the code easier to understand and maintain, and you can avoid duplication and repetition.

It is generally a good idea to embrace abstract functions when you want to write code that is flexible and reusable. For example, if you are writing a library or framework that needs to be applicable to different contexts or situations, or if you are writing a function that needs to be able to handle different types of inputs or arguments, an abstract function can be a good choice.

## Code Example 1 

To write abstract functional functions in JavaScript, you can use the function keyword to define a function, and use the this keyword to refer to the current object or context within the function. You can also use the apply() method to apply the function to different objects or contexts, and the call() method to call the function with specific arguments.

Here is an example of how you can write an abstract functional function in JavaScript:

```js
function myFunction() {
  // Use the `this` keyword to refer to the current object or context
  console.log(this.property);
}

// Apply the function to different objects or contexts
myFunction.apply({ property: 'value 1' }); // Outputs: "value 1"
myFunction.apply({ property: 'value 2' }); // Outputs: "value 2"

// Call the function with specific arguments
myFunction.call({ property: 'value 3' }); // Outputs: "value 3"
myFunction.call({ property: 'value 4' }); // Outputs: "value 4"
```

In this example, the myFunction() function is defined using the function keyword, and it uses the this keyword to refer to the current object or context within the function. The apply() and call() methods are then used to apply the function to different objects or contexts, and to call the function with specific arguments.

By using the function keyword, the this keyword, the apply() method, and the call() method, you can write abstract functional functions in JavaScript that can be applied to different objects or contexts, and that can be called with specific arguments.

## Code Example 2

```js
function add(x, y) {
  // Use the `this` keyword to refer to the current object or context
  return this.value + x + y;
}

// Apply the function to different objects or contexts
console.log(add.apply({ value: 10 }, [2, 3])); // Outputs: 15
console.log(add.apply({ value: 20 }, [4, 5])); // Outputs: 29

// Call the function with specific arguments
console.log(add.call({ value: 30 }, 6, 7)); // Outputs: 43
console.log(add.call({ value: 40 }, 8, 9)); // Outputs: 57
```

In this example, the add() function is defined using the function keyword, and it uses the this keyword to refer to the current object or context within the function. The add() function takes two arguments, x and y, and it returns the sum of the value property of the current object, x, and y.

## Code Example 3

```js
// Define an abstract function that takes a callback as an argument
function myFunction(callback) {
  // Use the `this` keyword to refer to the current object or context
  const data = this.getData(); // Get some data from the current object or context
  const result = callback(data); // Call the callback with the data as an argument
  return result; // Return the result of the callback
}

// Define a specific function that processes the data and returns a result
function myCallback(data) {
  // Process the data and return a result
  return data.map(item => item.value * 2);
}

// Apply the abstract function to different objects or contexts, and call the specific function with the data
const result1 = myFunction.apply({ getData: () => [{ value: 1 }, { value: 2 }] }, [myCallback]); // Outputs: [2, 4]
const result2 = myFunction.apply({ getData: () => [{ value: 3 }, { value: 4 }] }, [myCallback]); // Outputs: [6, 8]

// Call the abstract function with specific arguments and the specific function
const result3 = myFunction.call({ getData: () => [{ value: 5 }, { value: 6 }] }, myCallback); // Outputs: [10, 12]
const result4 = myFunction.call({ getData: () => [{ value: 7 }, { value: 8 }] }, myCallback); // Outputs: [14, 16]
```

The myFunction() function then calls the callback function with the data as an argument, and returns the result of the callback. This means that the myFunction() function is an abstract function that can be applied to different objects or contexts, and that can be called with different callback functions to process the data in different ways.

The myCallback() function is then defined as a specific function that processes the data and returns a result. The myCallback() function takes the data as an argument, and it processes the data by multiplying the value property of each item by 2.

The myFunction() and myCallback() functions are then used together to apply the myFunction() function to different objects or contexts, and to call the myFunction() function with specific arguments and the myCallback() function. In each case, the myFunction() function gets the data from the current object or context, and it calls the myCallback() function with the data as an argument. The myCallback() function then processes the data and returns the result, which is returned by the myFunction() function.


## When not to right abstract functions

> For example, if you are writing code that is specific to a particular situation or context, and you don't need to reuse the code in different contexts, an abstract function may be more complex and difficult to understand than a more concrete and specific function.