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Now we also learn about promises,

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often an alternative to working with callback functions,

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which you pass directly to the method

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that starts the async operation.

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Now in both scenarios, things can go wrong.

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Errors could occur.

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And since async operations

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work such that an operation is started

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and the code thereafter executes

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without waiting for that result,

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you can't use try catch here around your promise.

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So we can't do that here.

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I mean, we can write this code,

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but it won't work as intended.

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And we also can't do that if we use a callback function.

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Wrapping this with try catch also would not work as intended

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because try would only check if calling read file succeeds

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and not whether the result of read file is a success.

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That's why in case of the callback approach,

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we get this error parameter,

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which tells us whether an error occurred or not.

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And then we can always use a if check

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to see if error is set, if it's truthy as we learned,

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and then do something with it.

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That's something we can do to handle errors

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when working with callbacks.

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And I'll leave it at that dummy example here

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because we'll see better, more concrete examples

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in the later course sections.

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In case of promises, it's a bit different.

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Here in this anonymous function,

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we only get the data if the operation here

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reading the file succeeded.

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If that operation failed,

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we instead can add another method here

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to this promise chain and that's the catch method.

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Promises have a then method to handle the success case

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and catch to handle any errors

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that might've occurred in a previous promise.

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Catch also takes a function,

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but a function which gets that error object

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that describes the error that occurred.

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And then here we can console.log that error

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or handle it in any way we wanna handle it.

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And that's how you do handle errors

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with promises or callbacks.

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Again, we'll see better a little bit more concrete examples

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a little bit later in the course,

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but that's already the knowledge you need

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to understand how error handling will work later on.