What are higher-order functions in JavaScript?

Higher-order functions in JavaScript are defined as functions that can accept one or more functions as arguments or return a function as their result. This capability allows for a powerful style of programming where functions can be passed around and manipulated, leading to more abstract and concise code.

Using functions as first-class citizens, higher-order functions enable functional programming patterns. For example, functions like map, filter, and reduce in JavaScript are higher-order functions because they take a callback function as an argument to operate on each element of an array. This allows developers to write more flexible and reusable code, making it easier to handle complex operations or data manipulation without needing to redefine new functions repeatedly.

In contrast, the other concepts presented—functions that return multiple values, functions that convert strings to numbers, and functions that execute within the global scope—do not encompass the essence of higher-order functions. While they each represent valid programming functionality, they lack the specific characteristic of dealing with functions as inputs or outputs.