--- title: Let's keep it green ✅ | daily.dev description: A consultant shares a practical refactoring story: replacing Moment.js with Day.js to reduce bundle size. The approach involves three steps — centralizing... canonical: https://daily.dev/posts/let-s-keep-it-green--yrd5hqxhe twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Let's keep it green ✅ | daily.dev og:description: A consultant shares a practical refactoring story: replacing Moment.js with Day.js to reduce bundle size. The approach involves three steps — centralizing... og:url: https://daily.dev/posts/let-s-keep-it-green--yrd5hqxhe og:image: https://api.daily.dev/og/posts/yrD5hQXhE.png og:image:alt: Let's keep it green ✅ og:image:width: 1200 og:image:height: 630 og:locale: en --- [Playful Programming](https://daily.dev/sources/playfulprogramming) [Read post](https://api.daily.dev/r/yrD5hQXhE) # [Let's keep it green ✅](https://api.daily.dev/r/yrD5hQXhE "Go to post") This title could be clearer and more informative. Try out Clickbait Shield for free (5 uses left this month). A consultant shares a practical refactoring story: replacing Moment.js with Day.js to reduce bundle size. The approach involves three steps — centralizing library calls, writing tests to cover existing behavior, then swapping the library. The post emphasizes that a solid test suite is the foundation of safe refactoring, and demonstrates the bundle size improvement using rollup-plugin-visualizer. [#testing](/tags/testing "Check all #testing posts") Mar 16 • 2m read time • From [playfulprogramming.com](https://api.daily.dev/r/yrD5hQXhE "playfulprogramming.com") [](https://api.daily.dev/r/yrD5hQXhE "Go to post") Table of contents [Refactoring Copy link Link copied!](https://api.daily.dev/r/yrD5hQXhE?a=Refactoring "Refactoring Copy link Link copied!")[ Testing Copy link Link copied!](https://api.daily.dev/r/yrD5hQXhE?a=Testing "Testing Copy link Link copied!")[ A real example Copy link Link copied!](https://api.daily.dev/r/yrD5hQXhE?a=A-real-example "A real example Copy link Link copied!")[ Results 🚀 Copy link Link copied!](https://api.daily.dev/r/yrD5hQXhE?a=Results- "Results 🚀 Copy link Link copied!") Comment Bookmark Copy Share your thoughts Post Share this post [](https://daily.dev/sources/playfulprogramming) [Playful Programming](https://daily.dev/sources/playfulprogramming "https://daily.dev/sources/playfulprogramming") 7 Followers • 34 Upvotes #### Would you recommend this post? Copy link Slack WhatsApp Facebook X New Squad Copy linkShare with your friends ```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":"Let's keep it green ✅","url":"https://daily.dev/posts/let-s-keep-it-green--yrd5hqxhe","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/let-s-keep-it-green--yrd5hqxhe"},"datePublished":"2026-03-16T21:47:19.186Z","dateModified":"2026-03-16T21:58:17.563Z","description":"A consultant shares a practical refactoring story: replacing Moment.js with Day.js to reduce bundle size. The approach involves three steps — centralizing...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/4c061667de9ad02975ab9020d11a4810?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/4c061667de9ad02975ab9020d11a4810?_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/let-s-keep-it-green--yrd5hqxhe","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"testing","timeRequired":"PT2M"} {"@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":"Let's keep it green ✅"}]} ```