How To Debug js code in the board?

Thanks! I actually had call to use it in something this afternoon (debugging a temperature calculation) and it's already saved me a few minutes. Should have done it ages ago!

Calling foo(a,b) is treated as one step, is there a way to step into functions ?

Use step/s? That's the difference between step and next (next goes over functions)

What is difference between i l and i s ?

i l prints just the stuff local to that function

i s prints the whole scope chain (which could end up being big - hence you might not always want to do it)