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Lære Common Pitfalls in Synchronous Error Handling | Understanding and Handling Errors
Error Handling in JavaScript

bookCommon Pitfalls in Synchronous Error Handling

When handling errors in JavaScript, there are several common mistakes that you need to watch out for. One frequent pitfall is catching errors too broadly by wrapping large blocks of code in a single try statement. This practice can make it difficult to identify the true source of an error, and may lead you to miss important details about what went wrong.

Another issue is missing error sources entirely—if an error is thrown outside of a try block, it will not be caught, and your program may crash unexpectedly. Always ensure that you place your try blocks around the specific code that might throw, and be careful not to assume that every error will be caught simply because you used a try/catch structure.

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function processData(data) { // This error will NOT be caught by the try/catch below if (!data) { throw new Error("No data provided"); } try { // Only this code is protected let result = data.value * 2; console.log(result); } catch (error) { console.log("Caught an error:", error.message); } } processData(); // Throws "No data provided" and is NOT caught
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In the example above, the error is thrown before the try block begins. As a result, the catch clause never has a chance to handle the "No data provided" error, and the program will terminate with an uncaught exception. To fix this, you need to move the try block so that it surrounds all code that could potentially throw, including the initial check for data.

Note
Note

Always move your try block to surround all code that could throw errors, including initial checks, to ensure every error is handled gracefully and your code stays robust.

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What will happen when you run the code below?

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Seksjon 1. Kapittel 5

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bookCommon Pitfalls in Synchronous Error Handling

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When handling errors in JavaScript, there are several common mistakes that you need to watch out for. One frequent pitfall is catching errors too broadly by wrapping large blocks of code in a single try statement. This practice can make it difficult to identify the true source of an error, and may lead you to miss important details about what went wrong.

Another issue is missing error sources entirely—if an error is thrown outside of a try block, it will not be caught, and your program may crash unexpectedly. Always ensure that you place your try blocks around the specific code that might throw, and be careful not to assume that every error will be caught simply because you used a try/catch structure.

123456789101112131415
function processData(data) { // This error will NOT be caught by the try/catch below if (!data) { throw new Error("No data provided"); } try { // Only this code is protected let result = data.value * 2; console.log(result); } catch (error) { console.log("Caught an error:", error.message); } } processData(); // Throws "No data provided" and is NOT caught
copy

In the example above, the error is thrown before the try block begins. As a result, the catch clause never has a chance to handle the "No data provided" error, and the program will terminate with an uncaught exception. To fix this, you need to move the try block so that it surrounds all code that could potentially throw, including the initial check for data.

Note
Note

Always move your try block to surround all code that could throw errors, including initial checks, to ensure every error is handled gracefully and your code stays robust.

question mark

What will happen when you run the code below?

Select the correct answer

Alt var klart?

Hvordan kan vi forbedre det?

Takk for tilbakemeldingene dine!

Seksjon 1. Kapittel 5
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