What are Functions?

A function is like a little helper that you can ask to do a specific task for you in your code. It's a set of code that you can write once, and then use many times in your code.

function sayHello(name) {
  console.log("Hello, " + name + "!");
}

sayHello("Ram"); // Output: "Hello, Ram!"
sayHello("Laxman"); // Output: "Hello, Laxman!"

In more technical terms, they are a fundamental concept in programming that allows developers to write reusable pieces of code. A function is a block of code that performs a specific task and can be called from other parts of the program. Functions can take input, called arguments, and can return output or a value.

Sometimes, though, functions don't give you the expected result when you call them. Instead, they give you undefined . This happens when the function doesn't have a clear way to tell you the expected result.

Why does this happen?

It is like asking someone a question, but they don't give you an answer. You might get frustrated because you don't get back what the answer is, even though you asked the question. This is what exactly happens when a function returns undefined it's like the function doesn't have an answer for you, even though you asked it to do a specific task.

Here are a few reasons:-

Function without a return statement:

function addNumbers(a, b) {
  let sum = a + b;
}
let result = addNumbers(2, 3);
console.log(result); // undefined

In this example, the addNumbers function calculates the sum of two numbers, but it doesn't include a return statement. Therefore, when we call the function and try to store the result in a variable, we get undefined.

Function with an empty return statement:

function addNumbers(a, b) {
  let sum = a + b;
  return;
}
let result = addNumbers(2, 3);
console.log(result); // undefined

In this example, the addNumbers function calculates the sum of two numbers, but it has an empty return statement. This means that the function should return something, but it doesn't return the expected value. As a result, when we call the function and try to store the result in a variable, we get undefined.

Another reason for it might be Suppose that you have a function called getProductTotal that is used to calculate the total price of a product based on its price and quantity. The function this time has a return statement, but it returns undefined because it's trying to get a value that doesn't exist

function getProductTotal(price, quantity) {
  let totalPrice = price * quantity;
  let tax = getTaxRate(); // getTaxRate() is not defined
  return totalPrice + (totalPrice * tax);
}

let total = getProductTotal(10, 2);
console.log(total); // returns undefined

In this example, the getProductTotal function tries to get the tax rate by calling a function named getTaxRate, but here that function doesn't exist. So, the getProductTotal function can't calculate the total price of the product correctly and returns undefined.

These above examples show that how the functions might return undefined when they don't have correct and clear return statements. As a programmer, it's important for us to make sure that our functions always have correct and clear return statements so that we can get and use their results successfully.

Real-life examples to understand it

You ask your friend to tell you their favorite color, but they can't decide and they say "Ummm..." without telling you their favorite color. In this case, the function of "asking a favorite color" in technical terms returned undefined, because it didn't produce a clear and correct answer

You ask a friend to give you a pencil, but he/she doesn't have a pencil. When you ask them for the pencil, they will say "I don't have a pencil for you" which is like the function returning undefined because there is no value to give.

Recap

• Functions can return undefined if the return statement is missing.

• Functions can also return undefined if they have a return statement, but the value they are returning is undefined.

• This can happen if the function has a mistake in it, such as trying to get a value that doesn't exist.

• If a function returns undefined, it can cause errors in the program or unexpected behavior.

• To avoid this, it's important to make sure that functions always return the expected value, or at least have a default return value.

Thank you for reading, please give feedback if you think something can be improved.