What is the module pattern in JavaScript?
An IIFE that creates a private scope and returns an object with public methods. The private variables and methods are hidden inside the closure. Only the returned object is accessible from outside.
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More FAQs in Closures and Data Privacy in JavaScript
By declaring variables inside a function and returning methods that access them. The variables are in the function's lexical environment and cannot be accessed directly from outside, only through the returned methods.
No. ES2022 introduced #private class fields, which are truly private on class instances. But closures are still widely used for private state in non-class contexts and were the standard before private fields existed.
Closed-over variables are not garbage collected until the closure is (memory cost), private state is harder to test (you must go through the API), and you cannot inspect closed-over variables during debugging.
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