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  4. A Usable Node.js REPL for Emacs

A Usable Node.js REPL for Emacs

Jakub Holý user avatar by
Jakub Holý
·
Apr. 05, 15 · Interview
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Being used to the excellent REPL in Clojure(Script), I was surprised to find out that Node.js REPL is somewhat weak and that its support in Emacs is not actively maintained. I anyway managed to get a usable REPL with these three components:

  1. The Emacs nodejs-repl package (nearly 2 years old)
  2. J. David Smith’s nodejs-repl-eval.el to be able to send code to the REPL (binding nodejs-repl-eval-dwim to C-x C-e so that I can execute the current sexp/region)
  3. My own extension of nodejs-repl-eval.el that takes care of escaping JS constructs that the REPL interprets in a special way

Regarding #3: The problem with the Node.js REPL is that valid JS code does not always behave correctly in the REPL. This is because: 1) _ is a special variable (the last result) while in code it is often used for the underscore/lodash library; 2) The REPL also interprets lines somewhat separately and tries to execute <dot><name> as a REPL command, breaking chained calls that start on a new line. My solution uses some RegExp magic to turn

var _ = require("lodash"); // #1a conflicting use of _
_.chain([1,2])             // #1b conflicting use of _
   .first()                // #2 interpreted as non-existing REPL command '.first'
   .value();

into

var __ = require("lodash");  // #1a Notice the doubled _
__.chain([1,2]).             // #1b Notice the doubled _
   first().                  // #2 Notice the dot has moved to the previous line
   value();

when the code is being sent to the REPL

Emacs Node.js

Published at DZone with permission of Jakub Holý, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

Related

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  • Node.js: Architectural Gems and Best Practices for Developers to Excel
  • Using Render Log Streams to Log to Papertrail
  • How To Use the Node Docker Official Image

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