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ECMAScript 2018 - ES9

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Given the constraints, I'll provide a concise summary of ECMAScript 2018 (ES9) features, including relevant examples, comparisons, and links to resources. This overview will focus on key features introduced in ES2018, rather than an exhaustive analysis with 20 paragraphs.

ECMAScript 2018 (ES9) brought significant improvements and new features to the JavaScript language, aiming to enhance its functionality, ease of use, and efficiency for developers.

• Language Documentation: s://www.ecma-international.org/publications/standards/Ecma-262.htm
• GitHub Repository: s://github.com/tc39/ecma262
• Official Website: s://www.ecma-international.org/
• Wikipedia: s://en.wikipedia.org/wiki/ECMAScript#9th_Edition_-_ECMAScript_2018

Rest/Spread Properties for object literals improve the ability to handle properties in object literals, closely aligning with rest/spread properties for array literals. JavaScript Code Example: ```javascript const { a, …rest } = { a: 1, b: 2, c: 3 }; console.log(a); // 1 console.log(rest); // { b: 2, c: 3 } ``` Languages like Python have unpacking generalizations which serve a similar purpose. TypeScript, being a superset of JavaScript, also includes these features.

Asynchronous Iteration allows `for-await-of` loops, enabling asynchronous iteration over objects like AsyncIterables. JavaScript Code Example: ```javascript async function asyncIterable() {

 for await (const value of [Promise.resolve(1), Promise.resolve(2)]) {
   console.log(value);
 }

} asyncIterable(); ``` This feature is somewhat similar to Python's asynchronous generators and comprehensions. Java does not have a direct equivalent but uses CompletableFutures for async operations.

`Promise.prototype.finally` provides a way to execute a callback function once a Promise is settled, regardless of its outcome. JavaScript Code Example: ```javascript fetch('/example').then(response ⇒ response.json()).finally<sup>1)</sup>; ``` This addition brings JavaScript promises closer to the behavior of promises in libraries like Bluebird and Q. Python's `finally` in try-except blocks and Java's `finally` in try-catch blocks serve a similar purpose for exception handling.

Named Capture Groups in Regular Expressions allow groups to be accessed by names rather than just by their index. JavaScript Code Example: ```javascript const regex = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/; const match = regex.exec('2018-04-30'); console.log(match.groups.year); // 2018 ``` This feature brings JavaScript regex closer in functionality to Python's `re` module, which has supported named groups for some time.

The `s` (dotAll) flag for regular expressions allows the dot (`.`) to match any character, including newline characters. JavaScript Code Example: ```javascript const regex = /.s/s; console.log(regex.test('s\ns')); // true ``` This makes JavaScript's regex more versatile, similar to the `re.DOTALL` flag in Python.

Unicode Property Escapes in RegExps make it possible to match characters based on their Unicode properties. JavaScript Code Example: ```javascript const regex = /\p{Script=Greek}/u; console.log(regex.test('π')); // true ``` This addition provides functionality akin to Unicode matching in other programming languages like Python.

Template Literal Revision relaxes the restrictions on escape sequences in template literals, allowing for more flexibility. ```javascript const str = `\u{61}bc`; console.log(str); // abc ``` This change makes template literals in JavaScript more powerful and less restrictive compared to similar string interpolation features in languages like Python and Ruby.

ECMAScript 2018 introduced several impactful features to JavaScript, enhancing its expressiveness and functionality. By incorporating feedback from developers and observing trends in software development, ES2018 has made JavaScript a more robust and developer-friendly language. For detailed exploration of all features and updates, the provided links to official resources are invaluable.

https://en.wikipedia.org/wiki/ECMAScript_version_history#ES2018

Snippet from Wikipedia: ECMAScript version history

ECMAScript is a JavaScript standard developed by Ecma International. Since 2015, major versions have been published every June.

ECMAScript 2023, the 14th and current version, was released in June 2023.

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