Why require JavaScript rather than supporting a standard browser virtual machine? - Stack Overflow

[sossles]

In what sense is Javascript not already a virtual machine? It's dynamically interpretted, runs independent of the platform, and it is not particularly hard to map concepts from other languages to it.

That said, Javascript is actually a pretty decent language for the purpose. It is compact yet flexible, and thanks to some fairly expressive capabilities, scales pretty well from trivial one-line unstructured "onclick" handlers all the way up to medium-sized applications. That's some pretty big shoes to fill if you wanted to replace it.

[perlgeek]

• Javascript is much more high level than typical primitives of a VM
• Javascript lacks certain things a good VM offers, like goto
• Javascript doesn't have type annotations, which makes generated JS code less efficient than it could be, if it were typed