You could use (the compiled and optimized version of) the implementation we have in Scala.js: https://github.com/scala-js/scala-js/blob/master/library/src/main/

You could use (the compiled and optimized version of) the implementation we have in Scala.js: https://github.com/scala-js/scala-js/blob/master/library/src/main/scala/scala/scalajs/runtime/RuntimeLong.scala https://github.com/scala-js/scala-js/blob/master/library/src... It is significantly faster, especially for arithmetic operations, and dramatically so for division, remainder, as well as `toString()` (up to 100x speedup). It also contains the unsigned variant of operations (for java.lang.Lond.divideUnsigned for instance).