Self-Executing Anonymous Functions in JavaScript: Expression Parentheses vs. Invocation Parentheses?

Parentheses Placement in Self-Executing Anonymous JavaScript Functions

In JavaScript, anonymous functions can be self-executed by wrapping them in parentheses and appending an invocation operator at the end. However, there are two common ways to position the parentheses: around the function expression or around the function invocation.

Function Expression Parentheses

The older style, (function () { ... })(), wraps parentheses around the function expression. This approach creates a valid expression that evaluates to the undefined return value of the function.

Invocation Parentheses

The newer style, (function () { ... })(), wraps parentheses around the function invocation. This method executes the function and evaluates to undefined.

Difference and Usage

Both styles are functionally equivalent, resulting in the same undefined return value. There is no significant difference in memory consumption, as both cases create and execute an anonymous function.

The choice of parentheses placement is generally a matter of preference. However, it's worth noting that the second style is more common in modern JavaScript development and can help enhance code readability by visually separating the function declaration from its invocation.

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