Rob O'Dwyer

I’ve recently been working on a couple of small projects using Node.js, and I’m loving it’s simplicity and speed so far. One thing I have been missing though, thanks to my experience with Python and IPython, is the lack of a sane REPL for prototyping and testing out bits of code. I know, you can just run node and type stuff in, but the way that interpreter behaves is far from what I’d call “sane”. There’s no history, and if you screw up the order of brackets, or get lost in a multiline expression, you get to experience this wonderful prompt:

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> var x = function() {

[object Context]:1


...

Fortunately, the node.js docs suggest an alternative, using the handy rlwrap tool, which wraps any command inside a readline shell and gives you about a million options. I extended the provided example a bit, and ended up with this:

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alias node='env NODE_NO_READLINE=1 rlwrap -p Green -S "node >>> " node'

This tells node not to use it’s built-in readline functionality, replaces the prompt with a custom colored one, and automatically starts maintaining a history file for this command at ~/.node_history. Pretty fantastic. Although rlwrap does have some other options for messing around with alternate prompts, it looks like the simplest way of getting around node’s multiline REPL issues is to just use the built-in .break command. This seems to fix it in most cases.