How does an IIFE create data privacy in JavaScript?
By declaring variables inside the IIFE and returning an object with methods that access them. The variables are not accessible outside the IIFE, only through the returned methods. This is the module pattern.
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More FAQs in Block Scope and the IIFE Pattern in JavaScript
An Immediately Invoked Function Expression. It creates a new function scope immediately. Before ES6, it was used to create block-like scope for data privacy, to avoid global pollution, and to fix the var loop closure bug.
let is block-scoped and creates a fresh binding per iteration. Each callback closes over its own i, fixing the var loop closure bug without needing an IIFE. The IIFE was the pre-ES6 workaround.
Rarely. let and const provide block scope, ES modules provide module scope (no global pollution), and regular functions provide data privacy. IIFEs are mainly needed in old codebases that do not support ES6 or modules.
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