There are a few here's a list of some:

Crafty

MelonJS

LimeJS

These are all free, and seem fairly finished. I don't know much about the Lime and Melon, but Crafty has a decent community where you can get help in their forums. Which you choose depends on what you need.

There are a few here's a list of some:

Crafty (open source)

MelonJS (open source)

LimeJS (open source)

These are all free, and seem fairly finished. I don't know much about the Lime and Melon, but Crafty has a decent community where you can get help in their forums. Which you choose depends on what you need.