There is a web interpreter for JavaScript at www.squarefree.com which is just terrific. The up-arrow cmd history requires a backspace to edit ( at least in Opera ) but it is otherwise great.
It is the next best thing to running JavaScript persisted in a Smalltalk image.
But if you like a cool REPL for JS and are running even VisualStudio 2003 on .NET then you must compile the JScript ijs shell from the ListeningToReason blog.
Test either shell with
typeof Object(42)
and
Object(42).toString().length
or anything which you suspect might choke a toy Read-Eval-Print-Loop for JS.
Afterall, maybe you will find your inner Self in a LiveScript
I wouls be rmiss not to mention the Curl interpreter on the Web at the friedger site: it is an excellent way to experiment with Curl. Just enter some Curl in the bottom half of the split-pane and then click execute.
Try
{text This will display a |” \ “| character uninterpreted}