JavaScript Program: Handling TypeError with Try-Catch block

JavaScript Error Handling: Exercise-2 with Solution

Write a JavaScript program that uses a try-catch block to catch and handle a 'TypeError' when accessing a property of an undefined object.

Sample Solution:

JavaScript Code:

// Try block to handle potential errors
try {
  // Declare a constant variable undefinedObject and assign it the value undefined
  const undefinedObject = undefined;
  // Access a property of the undefined object, which will result in an error
  console.log(undefinedObject.property); // Accessing property of undefined object
} 
// Catch block to handle errors thrown in the try block
catch (error) {
  // Check if the error is an instance of TypeError
  if (error instanceof TypeError) 
  {
    // Log an error message indicating property access to an undefined object
    console.log('Error: Property access to undefined object');
  } 
  // If the error is not a TypeError, rethrow the error
  else 
  {
    throw error; // Rethrow the error if it's not a TypeError
  }
}

Output:

"Error: Property access to undefined object"

Note: Executed on JS Bin

Explanation:

In the above exercise, we create a variable undefinedObject and assign it the value of undefined. Then, we try to access undefinedObject's property. Since undefined has no properties, this operation will result in a TypeError.

The code is wrapped in a try-catch block. Inside the catch block, we check if the caught error is an instance of TypeError using the instanceof operator. If it is, we log the custom error message 'Error: Property access to undefined object'. Otherwise, if the error is not a TypeError, it might be a different type of error, so we rethrow the error using throw error.

Flowchart:

Live Demo:

See the Pen javascript-error-handling-exercise-2 by w3resource (@w3resource) on CodePen.

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