Why Do My Arrow Function Tests Fail When I Use Curly Brackets?

Curly Brackets in Arrow Functions

In a recent lecture, you encountered an interesting dilemma while working with arrow functions. Specifically, you discovered that tests failed when a particular function was written with curly brackets { }, whereas it worked correctly without them.

Understanding the Issue

Arrow functions can either have a concise body or a block body. When a function has a concise body, it consists of a single expression, and the result of that expression becomes the return value. In this case, the arrow function returns the result of the oneTodo function call without the need for an explicit return statement.

Adding Curly Brackets

When you added curly brackets, the function entered a block body, which requires an explicit return statement to specify the return value. As your code initially lacked this return statement, the function had an undefined return value, causing test failures.

Solution

To resolve the issue, you need to include an explicit return statement within the curly brackets:

(one) => {
  return oneTodo(one, action);
}

With this change, the function now explicitly returns the result of the oneTodo function call, even when written with curly brackets.

Summary

Understanding the difference between concise and block bodies in arrow functions is crucial to avoid confusion. By adhering to the correct syntax for each type of body, you can ensure that your functions behave as intended and pass all necessary tests.

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