--- title: IIFEs — a JavaScript Idiom of Yore | daily.dev description: IIFEs (Immediately Invoked Function Expressions) were a key JavaScript pattern before modern language features existed. This post explains what IIFEs are, why... canonical: https://daily.dev/posts/iifes-a-javascript-idiom-of-yore-bnyxwqa5e twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: IIFEs — a JavaScript Idiom of Yore | daily.dev og:description: IIFEs (Immediately Invoked Function Expressions) were a key JavaScript pattern before modern language features existed. This post explains what IIFEs are, why... og:url: https://daily.dev/posts/iifes-a-javascript-idiom-of-yore-bnyxwqa5e og:image: https://api.daily.dev/og/posts/BNYXWqA5e.png og:image:alt: IIFEs — a JavaScript Idiom of Yore og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # IIFEs — a JavaScript Idiom of Yore **[Playful Programming](https://daily.dev/sources/playfulprogramming)** · 4 min read · 0 upvotes · 0 comments ## Summary IIFEs (Immediately Invoked Function Expressions) were a key JavaScript pattern before modern language features existed. This post explains what IIFEs are, why they were used for scoping and aliasing in the absence of block scope, and how ES6+ features like `let`/`const`, modules, and top-level `await` have largely made them obsolete. It also covers the nuances of function statements in sloppy vs strict mode, and previews the stage-1 `do` expressions proposal as a cleaner alternative for inline value computation. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [IIFE for Complex Initialization](https://daily.dev/posts/iife-for-complex-initialization-cv3moacq5) · C\+\+ · 1 upvotes · 0 comments --- Tags: [#javascript](https://daily.dev/tags/javascript) [View this post on daily.dev](https://daily.dev/posts/iifes-a-javascript-idiom-of-yore-bnyxwqa5e) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"IIFEs — a JavaScript Idiom of Yore","url":"https://daily.dev/posts/iifes-a-javascript-idiom-of-yore-bnyxwqa5e","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/iifes-a-javascript-idiom-of-yore-bnyxwqa5e"},"datePublished":"2026-03-16T21:47:22.201Z","dateModified":"2026-03-16T21:55:49.280Z","description":"IIFEs (Immediately Invoked Function Expressions) were a key JavaScript pattern before modern language features existed. This post explains what IIFEs are, why...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/fb2433a508f5ed35bdc7c9c1676f1968?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/fb2433a508f5ed35bdc7c9c1676f1968?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Playful Programming","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Playful Programming","logo":"https://media.daily.dev/image/upload/s--WoGOmY81--/f_auto,q_auto/v1773697582/logos/playfulprogramming?_a=BAMAMiiu0","url":"https://daily.dev/sources/playfulprogramming"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/iifes-a-javascript-idiom-of-yore-bnyxwqa5e","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"javascript","timeRequired":"PT4M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Playful Programming","item":"https://daily.dev/sources/playfulprogramming"},{"@type":"ListItem","position":3,"name":"IIFEs — a JavaScript Idiom of Yore"}]} ```