Appendix A. An overview of ECMAScript

ECMAScript is a standard for scripting languages. ECMAScript syntax is implemented in several languages, the most popular implementation being JavaScript. The first edition of the ECMAScript specification was released in 1997, and the sixth edition was finalized in 2015. This edition is known as ES6 or ES2015. Lots of new features were introduced in ES6 compared to its predecessor ES5, and most of the syntax covered in this appendix is about the ES6 syntax. ES7 was finalized in 2016, and ES8 in 2017. ES7 and ES8 didn’t introduce many new syntax elements, but we’ll cover the async/await syntax from ES8 at the end of this appendix.

At the time of writing, most web browsers fully support the ES6 specification, ...

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