Check if a variable is of function type

In JavaScript, to check if a variable is a function, we typically use the typeof operator. For functions, typeof returns the string "function". This is a straightforward and general method that ensures the variable is indeed a function. Here is an example:

javascript
function exampleFunction() {
  console.log("Hello, World!");
}

var notAFunction = "I am a string";

// Check if exampleFunction is a function
if (typeof exampleFunction === "function") {
  console.log("exampleFunction is a function");
} else {
  console.log("exampleFunction is not a function");
}

// Check if notAFunction is a function
if (typeof notAFunction === "function") {
  console.log("notAFunction is a function");
} else {
  console.log("notAFunction is not a function");
}

In this example, exampleFunction is correctly identified as a function, while notAFunction is not. This approach is highly suitable for determining at runtime whether any given variable can be called as a function, thereby avoiding runtime errors.