ECMAScript is a standardized version of JavaScript with the goal of unifying the language's specifications and features. As all major browsers and JavaScript-runtimes follow this specification, the term ECMAScript is interchangeable with the term JavaScript.
Most of the challenges on freeCodeCamp use the ECMAScript 5 (ES5) specification of the language, finalized in 2009. But JavaScript is an evolving programming language. As features are added and revisions are made, new versions of the language are released for use by developers.
The most recent standardized version is called ECMAScript 6 (ES6), released in 2015. This new version of the language adds some powerful features that will be covered in this section of challenges, including:
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Arrow functions
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Classes
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Modules
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Promises
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Generators
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let and const
Not all browsers support ES6 features. If you use ES6 in your own projects, you may need to use a program (transpiler) to convert your ES6 code into ES5 until browsers support ES6.