Calling Node.Js Script from Rails App Using Execjs

ExecJS and could not find a JavaScript runtime

Ubuntu Users

I'm on Ubuntu 11.04 and had similar issues. Installing Node.js fixed it.

As of Ubuntu 13.04 x64 you only need to run:

sudo apt-get install nodejs

This will solve the problem.

CentOS/RedHat Users

sudo yum install nodejs

ExecJS::RuntimeError on Windows trying to follow rubytutorial

My friend was attempting a Rails tutorial on Win 8 RTM a few months ago and ran into this error. Not sure if this issue exists in Windows 7 as well, but this may help.

Options:

1) Removing //= require_tree . / Ignoring the issue - As ColinR stated above, this line should not be causing an issue in the first place. There is an actual problem with ExecJS working properly with the JavaScript runtime on your system and removing this line is just ignoring that fact.

2) Installing Node.js / Running away - Many people seem to just end up installing Node.js and using that instead of the JavaScript runtime already on their system. While that is a valid option, it also requires additional software and only avoids the original issue, which is that ExecJS is not working properly with the JavaScript runtime already on your system. If the existing JavaScript runtime on your system is supposed to work, why not make it work instead of installing more software? According to the ExecJS creator, the runtime already built into Windows is in fact supported...

ExecJS lets you run JavaScript code from Ruby. It automatically picks the best runtime available to evaluate your JavaScript program, then returns the result to you as a Ruby object.
ExecJS supports these runtimes:
therubyracer - Google V8 embedded within Ruby
therubyrhino - Mozilla Rhino embedded within JRuby
Node.js
Apple JavaScriptCore - Included with Mac OS X
Microsoft Windows Script Host (JScript)
(from github.com/sstephenson/execjs#execjs )

3) Actually fixing the issue / Learning - Use the knowledge of options 1 and 2 to search for other solutions. I can't tell you how many webpages I closed upon seeing options 1 or 2 was the accepted solution before actually finding information about the root issue we were having. The only reason we kept looking was that we couldn't believe the Rails team would (1) insert a line of code in every scaffold generated project that caused an issue, or (2) require that we install additional software just to run that default line of code. And so we eventually arrived at a fix for our root issue (your miles may vary).

The Fix that worked for us:
On the system having issues, find ExecJS's runtimes.rb file. It looks like this. Make a copy of the found file for backup. Open the original runtimes.rb for editing. Find the section that starts with the line JScript = ExternalRuntime.new(. In that section, on the line containing :command => "cscript //E:jscript //Nologo //U", - remove the //U only. Then on the line containing :encoding => 'UTF-16LE' # CScript with //U returns UTF-16LE - change UTF-16LE to UTF-8 . Save the changes to the file. This section of the file should now read:

JScript = ExternalRuntime.new(
    :name        => "JScript",
    :command     => "cscript //E:jscript //Nologo",
    :runner_path => ExecJS.root + "/support/jscript_runner.js",
    :encoding    => 'UTF-8' # CScript with //U returns UTF-16LE
)

Next, stop then restart your Rails server and refresh the page in your browser that produced the original error. Hopefully the page loads without error now. Here's the ExecJS issue thread where we originally posted our results: https://github.com/sstephenson/execjs/issues/81#issuecomment-9892952

If this did not fix the issue, you can always overwrite the modified runtimes.rb with the backup copy you (hopefully) made and everything will be back to square one. In that case, consider option 3 and keep searching. Let us know what eventually works for you.. unless it's removing the require_tree or installing node.js, there's plenty of that going around already. :)

Call Javascript from Rails 6 Service Object

You don't need to compile or transpile the Javascript if it's not running in the browser. You can send the data from Rails to Node by executing a shell script from Ruby.

In the Service Object (or Controller):

require "open3"
output, status = Open3.capture2("node ./lib/test.js", stdin_data: document)
# The `output` variable above will be returned with the content of `data` from the below script.
puts output

Script in /lib or /bin:

const fs = require('fs');

fs.readFile(0, 'utf8', function(err, data) {
  if (err) throw err;
  // do your proccessing here...
  console.log(data);
});