In the Node.js REPL, why does this happen?

Question

So I was playing around with the Node.js REPL and the Underscore library when I noticed something very strange. If I require("underscore"), the variable _ is set globally (obviously). Then when I attempt to run a simple command like console.log(_.isEmpty) it prints [Function] (again, obviously). However, upon running console.log(_) right after, it prints [Function] because the variable _ was set to _.isEmpty.

Why does this do this? If I run the same code from a js file this doesn't happen. Is this a normal Node thing or is this a total bug?

FYI: Node v0.10.10

See also [Using the Underscore module with Node.js](http://stackoverflow.com/q/5691901/1048572) — Bergi, Mar 02 '16 at 20:55

score 13 · Accepted Answer · answered Jun 12 '13 at 19:04

13

Node's REPL always sets _ to the result of the last line.

> 2
2
> _
2
> 2+2
4
> _
4
>

You need to use a different identifier:

var u = require("underscore");
u.isEmpty

answered Jun 12 '13 at 19:04

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So use underscore `.noConflict()` mode – Simon Boudrias Jun 12 '13 at 19:05
Wow had I just read the full documentation I would have figured that out. Thanks! Guess I'm not just crazy... – Tyler Johnson Jun 12 '13 at 19:08
1

With Node v6.0, the default behavior of `_` (underscore) is disabled when it is assigned to any value. A message shows "Expression assignment to _ now disabled." – abhisekp Apr 29 '16 at 02:46

In the Node.js REPL, why does this happen?

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