TypeScript Database Error Handling with custom class

TypeScript Error Handling : Exercise-7 with Solution

Write a TypeScript function that performs database operations. Create a custom error class, 'DatabaseError', for handling database-related errors. Use this error class to catch and log database errors.

Sample Solution:

TypeScript Code:

// Custom error class for database errors
class DatabaseError extends Error {
  constructor(message: string) {
    super(message);
    this.name = 'DatabaseError';
  }
}

// Simulated database operation function (replace with actual database operation)
function performDatabaseOperation(): Promise {
  return new Promise((resolve, reject) => {
    // Simulate a database error
    setTimeout(() => {
      reject(new DatabaseError('Database connection failed.'));
    }, 1000);
  });
}

// Function to perform database operations and handle errors
async function performDatabaseOperations(): Promise {
  try {
    await performDatabaseOperation();
    console.log('Database operation successful.');
  } catch (error) {
    if (error instanceof DatabaseError) {
      console.error(`Database Error: ${error.message}`);
    } else {
      console.error(`Unexpected Error: ${error.message}`);
    }
  }
}

// Execute the database operations and handle errors
performDatabaseOperations();

Explanations:

In the exercise above -

• First, we define a custom error class called 'DatabaseError' that extends the built-in Error class. It takes a custom error message as a parameter and sets the error name.
• The "performDatabaseOperation()" function simulates a database operation using a Promise and rejects it with a 'DatabaseError' containing a custom error message to simulate a database error.
• The "performDatabaseOperations()" function performs database operations using await and handles errors using a try-catch block. If a 'DatabaseError' is caught, it displays the custom database error message. Otherwise, it handles other unexpected errors.

Output:

Unexpected Error: Database connection failed.

TypeScript Editor:

See the Pen TypeScript by w3resource (@w3resource) on CodePen.

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