Changelog: “Exploring JavaScript” book

ES2025 edition

There is much new content in this edition:

• As every year: explanations of new ES2025 features
• HTML book: full-text search (above table of contents)
• Operators:
  • New section “Converting values to primitives”
  • Major rewrite of section on strict equality
  • Major rewrite of section on loose equality
    • New subsection section “How exactly does loose equality work?”
• Objects:
  • Section on structuredClone()
  • Major rewrite of section “Object literals: accessors”
  • New section “Objects with null prototypes make good dictionaries and lookup tables”
• Strings:
  • New long section: “Converting values to strings in JavaScript has pitfalls”
• Modules:
  • npm packages, package imports, package exports
  • module specifiers in browsers, using npm packages in browsers, import maps
  • Recommendations: named exports vs. default exports
• Arrays:
  • Improved section “Copying Arrays”
  • Improved section “.flatMap()”
  • Improved section “.reduce()”
• Sets:
  • Major rewrite of the whole chapter
• New chapter: “A roadmap for asynchronous programming”
  • (Extracted from chapter “Foundations of asynchronous programming in JavaScript”)
• Promises:
  • Major rewrite of section “The basics of using Promises”
  • New quick reference for the API
  • New section “Thenables (Promise-like objects)”
• Async functions:
  • Major rewrite of the whole chapter
  • New section “The pros and cons of return await”
• Regular expressions:
  • Major rewrite of the whole chapter
  • New section: “Tips for making regular expressions easier to use”
  • Better table: “Summary: .global (/g) and .sticky”
  • New quick reference for RegExp-related functionality.
• Classes:
  • Major rewrite of section “Subclassing”
  • Quick reference for Object.prototype.*
• Exception handling:
  • New section “Chaining errors: the instance property .cause”
• Typed Arrays:
  • New section “Converting a Uint8Array (UTF-8) to and from a string”

ES2024 edition

2024-09-03: * Fix names of exercise directories

2024-07-06: * Improve table showing the effects of the RegExp flags /g and /y * Add table for globalThis * “History and evolution of JavaScript”: improve FAQ and headings

2024-06-22: * ES2023 features: see chapter “New JavaScript features” * ES2024 features: see chapter “New JavaScript features” * Major rewrite of chapter on Arrays * Major rewrite of chapter on RegExps * Major rewrite of chapter on Promises * Major rewrite of chapter on Typed Arrays * Major rewrite of the chapter “Next steps” * Major rewrite of the section on the TC39 process, including an explanation of the new stage 2.7. * Quick references for Object.* and Reflect.* * Chapter on modules: * Explanation of re-exports * Improved cheat sheet * Chapter on classes: improved cheat sheet sheet * Many other improvements all over the book

ES2022 edition

• 2022-01-03:
  • Covered all new features of ES2022 (throughout the book): see chapter “New JavaScript features”
  • New cheat sheets (see chapters): strings, modules, objects, classes, Arrays
  • Major rewrites of chapter “objects” and chapter “classes”
  • Major rewrite of chapter “Exception handling”

ES2021 edition

• 2021-06-23:
  • Mentioned that ES2021 is a standard now.
  • Fixed broken image sources in HTML version.
• 2021-06-20: Improved content in section “Methods and the special variable this” in chapter “Single objects”.

2021-02-02 First release of ES2021 edition

• The exercises now run as native ESM modules on Node.js. Previously, they were run via the esm package.
• Material on new ES2021 features:
  • String.prototype.replaceAll()
  • Promise.any()
  • Logical assignment operators
  • Underscores (_) as separators in number literals and bigint literals
• New chapter: “New JavaScript features” lists what’s new in each release after ES6.
• Describing some features in more detail:
  • ES2019: New section on optional catch binding
  • ES2019: New section on Symbol.prototype.description
  • ES2018: New section on the template literal revision
  • ES2018: New section on Promise.prototype.finally()
  • ES2017: New section on trailing commas in function parameter lists and calls
• Rewrite of chapter “Callable values”:
  • Moved content on dynamic code evaluation into its own chapter.
  • Improved coverage of this
  • And more
• Rewrite of chapter “Single objects”:
  • Improved coverage of this
  • Explaining the function methods .call(), .apply(), .bind()
• Chapter on symbols:
  • Mostly new section “Symbols are primitives that are also like objects”
  • New section “The descriptions of symbols”
  • Major rewrite of section “Symbols as unique property keys”
• Chapter on regular expressions:
  • Much improved section “The flags /g and /y, and the property .lastIndex”

ES2020 edition

• 2020-06-23 First release of ES2020 edition:
  • Chapter “Operators”:
    • New section “The nullish coalescing operator (??) for default values”
  • New chapter: “Bigints – arbitrary precision integers”
    • Bigints are also mentioned throughout the book (primitive values, falsy values, etc.)
  • Chapter “Typed Arrays”:
    • New classes: BigInt64Array, BigUint64Array
    • New element types (e.g. in DataViews): BigInt64, BigUint64
  • Chapter “Modules“:
    • Rewritten section on import.meta.url
  • Chapter “Single objects”:
    • New section “Optional chaining for property accesses and method calls”
  • Chapter “Promises for asynchronous programming”:
    • New section “Promise combinators: working with Arrays of Promises”
  • Chapter “Regular expressions”:
    • New section “The flags /g, /y, and the property .lastIndex”
  • Omitted chapter: “Environments: under the hood of variables”
    • This chapter didn’t fit into the book anymore. I’ll try to publish it somewhere else, free online. And it remains available via the ES2019 edition.

ES2019 edition

• 2020-06-17 Last release of ES2019 edition:
  • Fixed line numbering in HTML
  • Fixed quiz question on WebAssembly speed
  • Deleted incorrect information on await-ing instances of Error
• 2020-06-15: Worked around an Apple Books bug with EPUB files
• 2019-08-31: Print edition