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In this section.

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Let's talk about how we can handle errors.

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In that way, we can send user friendly errors to the end user, or we will know the type of errors

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that might occur in our application.

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So let's answer to the question what is error handling?

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Here we go.

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It is a process of dealing with errors that occur during the execution of a program, or it is a way

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of preventing the program from crashing and allowing it to continue running smoothly.

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So that is what we call error handling.

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Before we can handle errors, we need to know the types of errors that might occur.

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And I have categorized them into two.

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The first one is what we call operational errors.

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So what is operational error?

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Well, operational errors are unexpected errors that occur when the express server is unable to start

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or shut down gracefully.

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So this has nothing to do with our code that we write or it is not due to our programming mistake.

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So operational errors are usually fatal and we prevent the express server from starting up.

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So this is what we call operational errors.

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The next type of error is what we call programming errors.

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Programming errors are caused by bugs in our code.

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They are not due to incorrect inputs or network issue or database and many more, but instead programming

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errors that can cause the program to crash, freeze or produce incorrect results.

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And this is what we call the programming errors.

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And these kind of errors are caused by the developers.

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Is something with the code that we write.

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So let's have a look at example of errors.

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And the each category is the first one and the operational error is what we call port conflict.

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When we say port conflict, it means that using one port for two or more applications, let's say that

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you are running React application and for React it is uses a port called 3000 and when developing your

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server or your back end, you are also using 3000 for the back end.

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If you use the same port, you're going to see a message that port is already in use and this kind of

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error is not due to us, but instead it is operational errors.

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The next one is what we call network issues, as the name implies.

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Next one is failed to connect to database and this one can due to network issue or invalid validation.

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The next type is what we call invalid path access, and the next one is database validation error.

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The next is unable to connect to the server.

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And lastly, request timeout.

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We have many of them, but these are examples of operational errors.

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So what about programming errors?

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Well, one example is attempting to use an undeclared variable, and sometimes it happens often.

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And then the next point is that forgetting to include a required file or module.

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The next point is passing the wrong data type to a function or a method.

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Let's say that we have created a function that takes in an array as an argument, but instead upon calling,

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we are passing in a boolean.

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In that way we are going to see on expected results.

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The next type of error is what we call performing an operation on incompatible data types.

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For example, you are adding boolean to an array.

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It's incompatible, right?

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So this kind of error is due to us.

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The next one is using an incorrect operator such as equal to instead of double equal to or triple equal

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to the next type is called forgetting to close a block of code with carry brackets.

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And these are all types of programming errors.

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And lastly, accidentally create an infinite loop.

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So these are types of errors that might.

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Okay, now that we know the overview or the types of errors in this video, let's see how we can handle

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errors in our express application step by step.