When Should I Use Explicit Return Statements in ES6 Arrow Functions?

When to Use Return Statements in ES6 Arrow Functions

ES6 arrow functions offer a concise syntax for writing functions. However, unlike traditional functions, arrow functions implicitly return the result of their expression.

When to Use Return

While implicit return is convenient, there are specific cases where an explicit return statement is necessary:

1. Multi-Line Functions

If an arrow function spans multiple lines, an explicit return statement must be used. This prevents errors if the developer forgets to add a return statement.

For instance, the following arrow function will return undefined if it expands to multiple lines:

(name) => {
  // Do something
};

To avoid this issue, an explicit return statement should be used:

(name) => {
  // Do something
  return 'Hi ' + name;
};

2. Blocks

When an arrow function includes a block (delimited by curly braces), an explicit return statement is required within the block.

For example, the following function will return undefined due to the lack of an explicit return statement:

(name) => {
  {
    return 'Hi ' + name;
  }
};

To fix this, an explicit return statement can be added:

(name) => {
  return {
    id: name
  };
};

Exceptions

There is one exception where an implicit return is valid within a block: when the block consists of a single expression enclosed in parentheses.

For example, the following function will return an object:

(name) => ({
  id: name
});

Examples

Here are some illustrative examples:

• Without Block: (name) => name; returns name.
• With Block and Explicit Return: (name) => { return 'Hi ' name; } returns 'Hi ' name.
• With Block and Implicit Return: (name) => ({ id: name }) returns { id: name }.
• With Error: (name) => { id: name } returns undefined due to the absence of an explicit return statement.

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