Arrow Functions and Curly Brackets: Implicit vs. Explicit Return?

Arrow Functions: The Curly Bracket Quandary

Dan Abramov's lectures and exercises provide a great learning experience. However, you may encounter a peculiar issue when using curly brackets in arrow functions. While the code works without these brackets, it fails when they are present.

The Reason:

The curly brackets create a block statement within the arrow function. This changes the behavior of the function, making it necessary to explicitly return a value using a return statement.

With Curly Brackets:

case 'toggleTodo' :
        return (
            state.map( (one) => {
                oneTodo( one, action )
            })
        );

In this example, the block statement requires a return statement for the function to return the oneTodo result.

Without Curly Brackets:

case 'toggleTodo' :
        return (
            state.map( (one) =>
                oneTodo( one, action )
            )
        );

When omitting curly brackets, the arrow function is considered to have a concise body. This means the oneTodo expression's result becomes the implicit return value.

To Resolve:

Ensure that when using curly brackets in arrow functions, you explicitly include a return statement to return the desired value.

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