The best replacement for actionscript is javascript.

The best alternatives to actionscript are rated as following:
★★★★★  javascript
★★  flex
★  haxe
★  mxml
★  processing
  typescript
  timeline
  ecmascript
  lingo
  tweening

Your alternative for actionscript is not listed? Suggest!
Speaking about actionscript, one probably shouldn't forget about flex.

Other search terms related to actionscript and their ratings are:
★★★★★ flex
★★★ mxml
★ flex tutorial
scaling
You have in mind a companion for actionscript and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of actionscript in all years. Click on graph for more.
actionscript
javascript
flex