Salesforce JavaScript Developer Practice Exam

What will be the output in the console for the provided code that attempts to reassign an imported module value?

1. TypeError: Property 'msg1' is read-only

2. Success: Variable has been reassigned

3. TypeError: Assignment to constant variable

4. ReferenceError: msg1 is not defined

The correct answer is: TypeError: Assignment to constant variable

In JavaScript, when you import a module, especially using the ES6 module syntax, the imported bindings are read-only and cannot be reassigned. This means that if the value that was imported is a constant or an object, you can’t change the reference to that object. If the code attempts to reassign an imported variable (in this case, `msg1`), JavaScript will throw a `TypeError`, indicating that you cannot assign a new value to a read-only property. The specific error message typically highlights that the assignment is being made to a constant variable, backing up the assertion that the import cannot be modified. This adheres to the rules governing module imports, which are designed to maintain immutability of the imported symbols. Thus, trying to change the value of an imported variable results in a clear error message, supporting the understanding that imports are designed to remain constant post-import. This principle fosters better modular design in JavaScript, preventing unintended mutations to values that should remain fixed.