What is the approach to achieve this nested function interface?

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The approach to achieve a nested function interface involves creating a function that returns another function. The returned function can then be executed to perform a specific task. This nesting can be repeated to create multiple layers of function interfaces, each with its own specific set of tasks.

For example, consider a simple function interface for calculating various mathematical operations:

function math() {
  return {
    add: function(x, y) {
      return x + y;
    },
    subtract: function(x, y) {
      return x - y;
    }
  }
}

The outer function math() returns an object with two functions add() and subtract(). Each of these functions takes two arguments and performs the respective mathematical operation. This is an example of a nested function interface as the add() and subtract() functions are wrapped inside the math() function.

To use this interface, one would simply call the math() function and then call the desired function from the returned object:

var result = math().add(2, 3);
console.log(result); // 5

Here, the add() function is called on the object returned by math(), passing in 2 and 3 as arguments. The function then returns the result of 2 + 3, which is 5.

This approach allows for a modular and extensible design, as new nested interfaces can be added as needed, each with its own set of functions and tasks.