4.0.0 • Public • Published


Node.js REPL with lodash

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animated gif showing usage of n_


Sometimes we use the Node.js REPL interface to experiment with code. Wouldn’t it be great to have that interface with lodash required by default?


$ npm install -g n_


$ n_
n_ >

lodash is now attached to the REPL context as _, so just use it:

n_ > _.compact([0, 1, false, 2, '', 3]);
[ 1, 2, 3 ]
n_ >

FP mode

It is possible to use lodash’s functional programming variant lodash/fp:

$ n_ --fp
n_ > _.map(function(v) { return v * 2; }, [1, 2, 3]);
[ 2, 4, 6 ]
n_ >

Strict mode

It is possible to enable strict mode in Node.js >= 4.x:

$ n_ --use_strict
n_ >

Repl specificities


Some commands are available to facilitate some operations, and are host under .lodash repl command:

  • .lodash fp: switch to lodash/fp
  • .lodash vanilla: switch to vanilla lodash mode
  • .lodash reset: switch to initial lodash mode
  • .lodash swap: switch to the other lodash mode (vanilla/fp)
  • .lodash current: output current lodash flavor in use
  • .lodash version: output lodash version in use

and the .lodash help to have more details about lodash repl commands

__ as last evaluated expression

Special character _ refer to the lodash instance, and cannot hold value of last expression. To provide the same feature, __ was introduced:

n_ > 10 + 2
n_ > 'number '+ __
'number 12'

Configuration options

Aside --fp and --use_strict/--use-strict, some other options are available either as CLI flags, or via environment variables.(with a trailing _N_)

The two main feature you can control is History persistance and Prompt Theme.

Flag aliases Env variable Description Default
--history-path --history, history-file _N_HISTORY_PATH Location of repl history file ~/.n_repl_history
--prompt.symbol _N_PROMPT__SYMBOL Symbol to use as $ prompt >
--prompt.name _N_PROMPT__NAME Name for the prompt n_
--prompt.color.name _N_PROMPT__COLOR__NAME Color for prompt name n_ blue
--prompt.color.symbol _N_PROMPT__COLOR__SYMBOL Color for prompt symbol red
--prompt.color.flavor _N_PROMPT__COLOR__FLAVOR Color for section of prompt about lodash flavor in use cyan
--prompt.color.help _N_PROMPT__COLOR__HELP Color for section of prompt about lodash flavor in use green

About styling, valid colors are: black, red, green, yellow, blue, magenta, cyan, white,gray, and dim.

Enjoy! 🚀

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  • jdalton
  • borisdiakur