[{"_1":2,"_3":-5,"_4":-5},"loaderData",{"_5":6,"_7":8},"actionData","errors","root",{"_28":-5,"_38":-5,"_39":40,"_41":42,"_43":44,"_45":46,"_47":48,"_49":50,"_51":52,"_53":54,"_55":56,"_57":58},"routes/_store+/_readers+/email_author.$slug/route",{"_9":10,"_11":-5},"book",{"_12":13,"_14":15,"_16":17,"_18":19,"_20":21,"_22":23},"currentUser","id","Z2lkOi8vbGVhbnB1Yi9TdG9yZTo6Qm9va1Byb2R1Y3QvMzcyMjY","title","You Don't Know JS Yet: Scope & Closures","state","published","contactAuthorMethod","email","aboutText","

The worldwide best selling You Don't Know JS book series is back for a 2nd edition: You Don't Know JS Yet. All 6 books are brand new, rewritten to cover all sides of JS for 2020 and beyond. You'll still get in-depth coverage of the core language, applied in useful code organization patterns for your programs. And of course, through Kyle's unique perspective and conversational tone, explore passionate, reasoned debate of the most common questions developers face.

Scope & Closures, the second book in the new edition series, dives deep into how and why to organize variables into different buckets of scope, limiting scope over-exposure and improving code maintainability. On top of lexical scope, closure empowers functions with memory, preserving variables across calls. Modules leverage scope and closures to encapsulate data and behavior.

In Scope & Closures, you'll dig into:

Nesting lexical scopes with functions and blocks, to limit scope exposure of variables
Functions remembering variables through closure
Modules, one of the most important code organization patterns in programming

~~~~

Frontend Masters is the premier sponsor of the 2nd edition of the *You Don't Know JS Yet* book series.

Frontend Masters helps you advance your skills with in-depth, modern front-end engineering courses, the highest quality video content available anywhere on the web. With over 150 courses to choose from, the expert content you need to take your development to the next level is here, so get started by joining today!

Among the amazing courses in the Frontend Masters library, Kyle's courses are the perfect companion materials to this book series. Check them all out, including these few specifically:

","authors",[24],{"_12":25,"_26":27,"_28":29},"Z2lkOi8vbGVhbnB1Yi9TdG9yZTo6UHJvZHVjdEF1dGhvci8zODkzNQ","name","Kyle Simpson","user",{"_30":31},"avatar",{"_32":33,"_34":35,"_36":37},"url","https://d39qdlcrvnra4b.cloudfront.net/avatars/247917/medium/kylesimpson2019-small.jpeg?1553868784","styleName","medium","exists",true,"shoppingCartId","shoppingCart",{"_12":71,"_72":73,"_74":37,"_75":76,"_77":78,"_79":80,"_81":37},"locale","en","readerTheme","light","constants",{"_69":70},"publishers",{"_65":66,"_67":68},"learnerOrganizations",[],"needsLocaleCookieSync",false,"announcements",{"_59":60,"_61":-5},"sentryEnvironment","production","sentryRelease","4b9cc63097cd4c67d0cc0e1eb59a0e1651432dfc","announcement_store",{"_62":37,"_63":64},"announcement_authors","flag","text","

Kick off your book project, get started with GhostAI, get better at marketing, or spend the day doing all three! Free live workshops on Zoom. Saturday, June 27, 2026.

\n","companies",[],"universities",[],"paypalClientId","AX53Cwz8jR6rVVzzZiZNWWXl0dGagi-GZrjG-S3Ua14E5nrKMn7DxDQ730O4R8LusLPp49ALn6aRVaEy","no-cart","count",0,"free","updatedAt","","paymentGateway","STRIPE","cartItems",[],"loading"]

Email the Author