Some languages that compile to javascript

Most of these untested by me.

Scala.js Scala.js

Clojurescript clojure/clojurescript: Clojure to JS compiler

Numbers

    ClojureScript currently only supports integer and floating point literals that map to JavaScript primitives
        Ratio, BigDecimal, and BigInteger literals are currently not supported
        Equality on numbers works like JavaScript, not Clojure: (= 0.0 0) => true

Kotlin JavaScript Interop | Kotlin Blog

Nim Nim Backend Integration

Features or modules that the JavaScript platform does not support are not available. This includes:

    manual memory management (alloc, etc.)
    casting and other unsafe operations (cast operator, zeroMem, etc.)
    file management
    most modules of the Standard library
    proper 64 bit integer arithmetic
    unsigned integer arithmetic

Dart