JavaScript Program: Handling URIError with Try-Catch block for invalid URI decoding

JavaScript Error Handling: Exercise-9 with Solution

Handle URIError for Invalid URI

Write a JavaScript program that uses a try-catch block to catch and handle a `URIError` when decoding an invalid URI.

Sample Solution:

JavaScript Code:

// Define a function named decode_URI_String that takes a parameter uriString
function decode_URI_String(uriString) {
  // Attempt to decode the URI string
  try {
    // Decode the URI string
    const decodedURI = decodeURI(uriString);
    // Log the decoded URI to the console
    console.log('Decoded URI:', decodedURI);
  } catch (error) {
    // If an error occurs during execution
    // Check if the error is a URIError
    if (error instanceof URIError) {
      // If the error is a URIError, log the error message with 'URIError' prefix
      console.log('URIError:', error.message);
    } else {
      // If the error is not a URIError, log the error message with 'Error' prefix
      console.log('Error:', error.message);
    }
  }
}

// Example:
// Call the decode_URI_String function with a valid URI string
decode_URI_String('https://example.com/'); // Valid URI
// Call the decode_URI_String function with an invalid URI string containing special characters
decode_URI_String('https://example.com/%%invalidURI'); // Invalid URI

Output:

"Decoded URI:"
"https://example.com/"
"URIError:"
"URI malformed"

Note: Executed on JS Bin

Explanation:

In the above exercise -

• The "decodeURIString()" function attempts to decode the provided URIString using the decodeURI function within a try block.
• If the URI is valid, the decoding process will succeed, and the decoded URI will be logged to the console.
• However, if the URI is invalid, a URIError will be thrown. We catch this error in the catch block and check if the error is an instance of URIError using the instanceof operator.
• If it is a URIError, we log a message with the prefix 'URIError:' followed by the error message. Otherwise, for other types of error, we log a message with the prefix 'Error:' followed by the error message.

Next we call the “decodeURIString()” function twice. The first call with a valid URI 'https://example.com/' will decode successfully and print the decoded URI to the console.

The second call with an invalid URI 'https://example.com/%%invalidURI' will throw a URIError due to invalid characters. The catch block will handle this error and print a message indicating the URIError.

Flowchart:

Live Demo:

See the Pen javascript-error-handling-exercise-9 by w3resource (@w3resource) on CodePen.

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