Lære Best Practices for Resilient Code | Debugging and Writing Resilient Code

When you aim to write resilient JavaScript code, following a set of proven best practices is crucial for reducing bugs and making your code easier to maintain. Three key practices stand out:

Providing specific error messages;
Keeping the scope of try/catch blocks minimal;
Implementing graceful degradation.

Specific error messages help you and others quickly identify what went wrong and where, making debugging far simpler.

Keeping the scope of try/catch blocks as small as possible ensures that you catch only the errors you expect and avoid masking unrelated bugs.

Graceful degradation means your code continues to function—at least partially—even when something goes wrong, rather than failing completely.


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function processUserInput(input) {
  // Validate input type first
  if (typeof input !== "string") {
    throw new TypeError("Input must be a string");
  }

  // Minimal try/catch scope: only wrap the code that might throw
  try {
    // Simulate parsing user data
    const data = JSON.parse(input);

    // Check for required property
    if (!data.username) {
      throw new Error("Missing required property: username");
    }

    // Return processed result
    return `Welcome, ${data.username}!`;
  } catch (err) {
    // Graceful degradation: return a user-friendly message
    return `Could not process input: ${err.message}`;
  }
}

In the processUserInput function, each best practice is applied directly.

The code checks the input type before any risky operations, and if the type is incorrect, it throws a TypeError with a clear, specific message—demonstrating the importance of precise error reporting;
The try/catch block is kept minimal, wrapping only the code that might throw due to parsing or missing properties, which keeps unrelated errors outside its scope;
If any error occurs, the catch block returns a user-friendly message instead of letting the entire operation fail, ensuring graceful degradation so your application can continue running even in the face of unexpected input.

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