Determining if a Value is a Function in JavaScript

This challenge focuses on accurately identifying whether a given value in JavaScript is a function. Understanding how to reliably check for functions is crucial for dynamic code execution, event handling, and ensuring the correct type of arguments are passed to operations. Your task is to write a function that returns true if the input is a function and false otherwise.

Problem Description

You are required to create a JavaScript function named isFunction that accepts a single argument, value. This function should determine if value is a function. The function should return true if value is a function and false otherwise. You should leverage JavaScript's built-in typeof operator and the Function constructor to achieve this.

Key Requirements:

• The function must be named isFunction.
• It must accept a single argument, value.
• It must return a boolean value (true or false).
• The solution should be robust and handle various input types correctly.

Expected Behavior:

The function should correctly identify functions defined using various methods, including:

• Function declarations (e.g., function myFunction() {})
• Function expressions (e.g., const myFunction = function() {};)
• Arrow functions (e.g., const myFunction = () => {};)
• Methods of objects (e.g., obj.myMethod = function() {};)

It should return false for non-function values, such as:

• Numbers
• Strings
• Booleans
• Arrays
• Objects (that are not functions)
• null
• undefined

Edge Cases to Consider:

• typeof null returns "object", so you must account for this.
• Consider the behavior with Function constructor.

Examples

Example 1:

Input: function() {}
Output: true
Explanation: The input is a function declaration.

Example 2:

Input: () => {}
Output: true
Explanation: The input is an arrow function expression.

Example 3:

Input: "hello"
Output: false
Explanation: The input is a string, not a function.

Example 4:

Input: null
Output: false
Explanation: The input is null, which typeof returns "object" but is not a function.

Example 5:

Input: 123
Output: false
Explanation: The input is a number, not a function.

Constraints

• The function must be written in JavaScript.
• The function must not use any external libraries or frameworks.
• The function should be efficient and avoid unnecessary computations.
• The input value can be of any JavaScript data type.

Notes

Think about how typeof behaves with different data types, especially null. The Function constructor can be helpful in distinguishing between objects that are functions and those that are not. Consider using a combination of typeof and a check against the Function constructor to ensure accuracy.