Function Composition
Function composition allows us to combine multiple functions into a single function, where the output of one function becomes the input of the next.

In the above example, add, multiplyBy2, and subtract are high-order functions that return functions as results. The composedFunction combines these functions to perform a series of operations on the input x.

Callbacks
Callbacks are commonly used with high-order functions to handle asynchronous operations.

In this example, delayedGreeting is a high-order function that takes a name and a callback function. It uses setTimeout to simulate a delay and invokes the callback with the greeting message after the specified time.

Filtering and Transformation
High-order functions like map, filter, and reduce are frequently used for data manipulation and transformation. Here's an example using Python:

In the above examples, the filter function filters out even numbers, the map function transforms each number to its square, and the reduce function calculates the sum of all numbers in the list.

These examples demonstrate how high-order functions provide flexibility and abstraction, allowing us to perform powerful operations with concise and reusable code.