While Python may be an easy language, Javascript may be the easiest to get things running. It's just there before you even start downloading what other languages need. Just press F12 and REPL away. I use the JS console as a calculator on steroids among other things. It's nice that it has the C family syntax, which lets me interactively test expressions before using them on non-browser code, without the prerequisite of projects, files or other boilerplate.