It would be great if the list could rank how "well" these languages compile to JavaScript along some metrics:<p>- How much functionality remains in JavaScript vs the most-supported platform<p>- How many language bugs there are in JavaScript vs the most-supported platform by running a large testsuite (e.g. all tests of all public packages)<p>- How large the JS "binary" is, how long it takes to load (many languages put their entire VM into the JavaScript)<p>- How well the language interops with HTML / DOM (can you make usable websites with it? How about static sites with embedded content as opposed to React-style webapps?)<p>- <i>How well the language interops with JavaScript libraries (npm)</i><p>Because there are a lot of languages which claim to compile to JavaScript but my experience is that many are unfortunately not practical due to issues with the above.<p>By far the most popular JS-target language is TypeScript, in part because it integrates <i>very</i> seamlessly being essentially JavaScript with optional type annotations. There are other contenders which also integrate well enough to be practical and which are used in large-scale projects (Elm, Scala.js, Dart). But I know that some the languages and compiling tools listed don't work very well and have major limitations.