Exit Function (Javascript)
Published: 2023-02-28 10:59:06

As **developers** (a.k.a pro googlers), we all know how frustrating it can be to write code that doesn’t work as intended. We might spend hours trying to debug our code, only to find that a small typo or a misplaced semicolon was the culprit. That’s where the exit function comes in handy.

## What is the Exit Function in JavaScript?
Think of the exit function as your emergency exit from a function. It’s like when you’re at a party and you suddenly realize you have to leave because you forgot to turn off the stove (yes, it happens!). You don’t want to waste any more time at the party, you just want to leave immediately. That’s what the exit function does — it lets you exit a function immediately and return a value to the caller. Cool, right?

Let’s take a look at an **example**. Imagine you’re writing a function to calculate the area of a rectangle. You might write something like this:

```
function calculateArea(length, width) {
  let area = length * width;
  return area;
}
```
But what happens if the user enters a negative value for either length or width? Your function will still calculate the area, but it won’t be a valid value. That’s where the exit function comes in.

You can modify the function to check for negative values and exit early if they’re found:

```
function calculateArea(length, width) {
  if (length < 0 || width < 0) {
    return "Error: Length and width must be positive values.";
  }
  let area = length * width;
  return area;
}
```
Now, if the user enters a negative value for either length or width, the function will exit immediately and return an error message. No more wasting time calculating the area of an invalid rectangle! Yay!

Here’s a more complex example that demonstrates how you can use the exit function to return a function from another function (huh?):

```
function createCalculator(operator) {
  if (operator === "+") {
    return function add(num1, num2) {
      return num1 + num2;
    }
  } else if (operator === "-") {
    return function subtract(num1, num2) {
      return num1 - num2;
    }
  } else {
    return function() {
      return "Error: Invalid operator.";
    }
  }
}
```
In this example, we’re defining a function called createCalculator that takes an operator as a parameter. If the operator is "+" or "-", the function returns a function that adds or subtracts two numbers, respectively. If the operator is neither "+" nor "-", the function returns an error message.

**TESTING TIME!** Let’s test this function with some examples:

```
const addNumbers = createCalculator("+");
console.log(addNumbers(2, 3)); // Output: 5

const subtractNumbers = createCalculator("-");
console.log(subtractNumbers(5, 3)); // Output: 2

const divideNumbers = createCalculator("/");
console.log(divideNumbers(10, 2)); // Output: Error: Invalid operator.
```
As you can see, when we call `createCalculator` with the "+" operator, it returns a function called add that adds two numbers. Similarly, when we call `createCalculator` with the "-" operator, it returns a function called subtract that subtracts two numbers.

However, when we call `createCalculator` with the "/" operator, it doesn't return a function that can divide two numbers. Instead, it `returns` a function that simply returns an error message.

In conclusion, the exit function in JavaScript can be a lifesaver when you need to exit a function early and return a value to the caller. By using the exit function creatively, you can write more efficient and flexible code that can handle a variety of use cases.

If you enjoyed this article and want to learn more about JavaScript or programming in general, be sure to follow me for more helpful tips and tricks. Happy coding!