In JavaScript, returning a function (or an object containing functions) from another function allows us to expose methods that can be accessed and used outside the scope of the parent function. This approach is useful for encapsulating logic and creating reusable components.

Example:

var expect = function(val) {
    function toBe(num) {
        if (num === val) {
            return true;
        } else {
            throw new Error("Not Equal");
        }
    }
    function notToBe(num) {
        if (num !== val) {
            return true;
        } else {
            throw new Error("Equal");
        }
    }
    return { toBe, notToBe };
};

Explanation:

• Encapsulation: By returning an object containing toBe and notToBe, we encapsulate these methods within the expect function, providing a clean and organized structure.
• Accessibility: Returning the functions makes them accessible from outside the expect function, allowing us to use them as methods on the returned object.
• Reusability: This pattern allows us to create reusable and composable functions that can be easily integrated into different parts of an application.

By returning the functions, we can create flexible and maintainable code that adheres to the principles of modularity and separation of concerns.