ECMA International — The organization that includes the group that works on ECMAScript.
TC39 — The group within ECMA that works on the ECMAScript standard.
ECMAScript 5 — The version fully supported by most browsers
ECMAScript 2015 / ECMAScript 6 / ES.Next / ES Harmony — Final Draft standardized June 2015, becoming the new 'current version'. Support for its features is still building up among browser vendors.
Browser compatibility table — Includes ECMAScript 5, 6, and 7 compatibility
TypeScript — Has strong typing. C# and Java developers will be comfortable with TypeScript syntax, but people who are already JS developers will favor TypeScript the most. If you prefer compile-time type checking and looking at type information, or you have a lot of type-related bugs, you should use TypeScript. If you won't use type annotations, just use ES6. Current version: 1.5
Haxe — An older project that began in 2006 and now compiles to nine languages including JS. Haxe takes the 'fixing JS' approach and follows the behaviors used by other popular languages like Java/C#. It also brings in many advanced functional programming concepts. Haxe will be popular among developers of those languages, while JS developers will be more at home with TypeScript. TypeScript vs. Haxe Comparison - Changelog
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