Error Handling

Exceptions in JavaScript are events that disrupt the normal flow of code execution when an error occurs.

When an exception is thrown, the normal flow of the program is interrupted, and control is transferred to the nearest enclosing try...catch block that can handle the exception.

JavaScript exceptions can be divided to 2 categories: built-in exceptions (Error, TypeError, ReferenceError, SyntaxError etc.) and custom exceptions, that can be created using the throw statement.

throw Statement

function getAccess(age) {
  if (age < 18) {
    throw new Error('You must be at least 18 years old.');
  }
  return 'Access granted';
}

try...catch Statement

JavaScript provides mechanisms to handle runtime errors using try...catch blocks.

function tryToGetAccess() {
  try {
    const result = getAccess(age);
    console.log(result);
  } catch (error) {
    console.error('An error occurred:', error.message);
  } finally {
    console.log('This will run regardless of the try/catch result.');
  }
}

tryToGetAccess(20); // Access granted

tryToGetAccess(16); // An error occurred: You must be at least 18 years old

• If getAccess() runs without errors, Access granted is logged to the console.

• If getAccess() throws an error, the catch block logs the error message to the console.