I have a Rails application that needs to run a node script. I imagine that using the ExecJS gem is the cleanest way to run JavaScript from a Rails app. However, so far, ExecJS has proved to be very frustrating to use.
Here is the script I need to run:
// Generated by CoffeeScript 1.7.1
(function() {
var PDFDocument, doc, fs;
fs = require("fs");
PDFDocument = require('pdfkit');
doc = new PDFDocument;
doc.pipe(fs.createWriteStream('output.pdf'));
doc.addPage().fontSize(25).text('Here is some vector graphics...', 100, 100);
doc.save().moveTo(100, 150).lineTo(100, 250).lineTo(200, 250).fill("#FF3300");
doc.scale(0.6).translate(470, -380).path('M 250,75 L 323,301 131,161 369,161 177,301 z').fill('red', 'even-odd').restore();
doc.addPage().fillColor("blue").text('Here is a link!', 100, 100).underline(100, 100, 160, 27, {
color: "#0000FF"
}).link(100, 100, 160, 27, 'http://google.com/');
doc.end();
}).call(this)
From my Rails console, I try this:
[2] pry(main)> file = File.open('test.js').read
[3] pry(main)> ExecJS.eval(file)
ExecJS::ProgramError: TypeError: undefined is not a function
from /Users/matt/.rvm/gems/ruby-2.1.0/gems/execjs-2.0.2/lib/execjs/external_runtime.rb:68:in `extract_result'
Note that I can run this script successfully using 'node test.js' and I am also able to run run the script using the backtick syntax Ruby offers:
`node test.js`
But that feels like a hack...
It's erroring out because require() is not supported by EvalJS. 'require' is undefined, and undefined is not a function. ;)
I'm not sure of the answer but maybe you need to precise the exec_js_runtime environment variable to be node.
Something like ENV['EXECJS_RUNTIME'] = 'Node' You can try to put it in the config/boot.rb or just to define the EXECJS_RUNTIME in your environment, something like export EXECJS_RUNTIME=Node
Hope it helps
ExecJS people say use commonjs.rb https://github.com/cowboyd/commonjs.rb
Why can't I use CommonJS require() inside ExecJS?
ExecJS provides a lowest common denominator interface to any
JavaScript runtime. Use ExecJS when it doesn't matter which JavaScript
interpreter your code runs in. If you want to access the Node API, you
should check another library like commonjs.rb designed to provide a
consistent interface.
But this doesn't work basically. The require acts completely erratically - I had to execute npm -g install pdfkit fs between env = and env.require in
require 'v8'
require 'commonjs'
env = CommonJS::Environment.new(V8::Context.new, path: ::Rails.root )
env.require 'script'
for the module lookup to work O.o and if I tried pointing path to the node_modules folder then it would be impossible for the gem to find script (not to mention that the #new and require are basically the only documented methods - only methods afaik - and #new is misdocumented :P)
Your options as far as I can tell:
system(node ...) - you can use Cocaine to escape some gotcha's (piping output, error handling, performance tweaks, ...) and run a cleaner syntax - this is not as bad as it looks - this is how paperclip does image postprocessing (imagemagick system package + cocaine) so I guess it's very stable and very doable
expose to web api and run a separate worker on a free heroku dyno for example to do this and similar stuff you want to do with node libs
use prawn :)
Get rid of ExecJS and anything that depends on ExecJS. I tried all the other suggestions, but this actually fixed it.
ES6 has been around since 2015. Any tool worth using supports it by now. MICROSOFT EDGE supports it by now. Seriously.
Related
First things first. I know that there are other questions that are similar to this e.g. use NodeJs Buffer class from client side or
How can I use node.js buffer library in client side javascript
However, I don't understand how to make use of the reference to use browserify though it is given approval.
Here is my Node code:
import { Buffer } from 'buffer/';
I know this is the ES6 equivalent of require.
I would like a javaScript file implementation of this module so that I can simply use the standard html file reference:
<script src=./js/buffer.js></script>
And then use it as in for example
return new Buffer(temp).toString('utf-8');
This simply falls over with the
Uncaught ReferenceError: Buffer is not defined
no matter how I create the buffer.js file.
So using the browserify idea I've tried using the standalone script (from the https://www.npmjs.com/package/buffer as https://bundle.run/buffer#6.0.3 )
I've created a test.js file and put
var Buffer = require('buffer/').Buffer
in it and then run browserify on it as
browserify test.js -o buffer.js
and many other variations.
I'm not getting anywhere. I know I must be doing something silly that reflects my ignorance. Maybe you can help educate me please.
These instructions worked for me. Cheers!
Here are the instructions you can look at the web section.
https://github.com/feross/buffer
Here is what the instructions state about using it in the browser without browserify. So from what you tried
browserify test.js -o buffer.js
I would just use the version directly that does not require browserify
To use this module directly (without browserify), install it:
npm install buffer
To depend on this module explicitly (without browserify), require it like this:
var Buffer = require('buffer/').Buffer // note: the trailing slash is important!
I am just re-looking at Jest as it's been getting a lot of good reports. However struggling to find a good way the access internal functions to test them.
So if I have:
const Add2 = (n)=> n+2;
export default (list)=>{
return list.map(Add2());
}
Then if I was using Jasmine or Mocha I'd use rewire or babel-plugin-rewire to get the internal Add2 function like this:
var rewire = require('rewire');
var Add2 = rewire('./Adder').__get__('Add2');
it('Should add 2 to number', ()=>{
let val = Add2(1);
expect(val).toEqual(3);
});
However neither of them seem to work with jest and while there looks like an excellent mocking syntax I can't see any way to get internal function.
Is there a good way to do this, something I'm missing on the jest api or set up?
You can actually achieve this if you are willing to use babel to transform your files before each test. Here's what you need to do (I'll assume you know how to get babel itself up and running, if not there are multiple tutorials available for that):
First, we need to install the babel-jest plugin for jest, and babel-plugin-rewire for babel:
npm install --save-dev babel-jest babel-plugin-rewire
Then you need to add a .babelrc file to your root directory. It should look something like this:
{
"plugin": ["rewire"]
}
And that should be it (assuming you have babel set up correctly). babel-jest will automatically pick up the .babelrc, so no additional config needed there unless you have other transforms in place already.
Babel will transform all the files before jest runs them, and speedskater's rewire plugin will take care of exposing the internals of your modules via the rewire API.
I was struggling with this problem for some time, and I don't think the problem is specific to Jest.
I know it's not ideal, but in many situations, I actually just decided to export the internal function, just for testing purposes:
export const Add2 = x => x + 2;
Previously, I would hate the idea of changing my code, just to make testing possible/easier. This was until I learned that this an important practice in hardware design; they add certain connection points to their piece of hardware they're designing, just so they can test whether it works properly. They are changing their design to facilitate testing.
Yes, you could totally do this with something like rewire. In my opinion, the additional complexity (and with it, mental overhead) that you introduce with such tools is not worth the payoff of having "more correct" code.
It's a trade-off, I value testing and simplicity, so for me, exporting private functions for testing purposes is fine.
This is not possible with jest. Also you should not test the internals of a module, but only the public API, cause this is what other module consume. They don't care how Add2 is implemented as long as yourModule([1,2,3]) returns [3,4,5].
I am looking for a simple git-like cli argument parser like this:
$ app [global-options] command [command-options]
I tried commander, gitlike-cli, and few other cli parser libs---none of them seem to support segregation of global options from command-options.
commander seems to be supporting it. But when I delved deeper, I found issues. For example, I wanted a -v global option that would enable verbosity at global level. All I did was to set global.verbose = true; in index.js, and in the command specific index-subcmd.js, when I read global.verbose, it is not set!
Am I missing something obvious, or is my understanding correct that node ecosystem is lacking a lib with this functionality? Coming from Java background, I really miss airline.
I wrote a cli parsing library to support the usecase: wiz-cliparse.
I would also like to point out a library I wrote after being disappointed with the popular CLI tools. I created wily-cli to compete against those big name tools by providing more customization and CLI features, and attempting to be easier to use. Subhash's wiz-cliparse should definitely be able to help your use case, but if you need to create a more powerful CLI, I might recommend looking into wily-cli. For your use case, those "global options" would essentially be the the options of your initial command (from your example, that would be app). When creating an option, you would set the passThrough flag in the option configuration...
.option('example', 'Example option', { passThrough: true });
This will set the option to also be passed down to children/gandchildren/etc. commands
I've come across an interesting problem in NodeJS that pops up now and then at work, and I haven't been able to figure it out.
I've written a back-end in CoffeeScript, which I then compile with grunt-contrib-coffee into Javascript in a ~/bin directory. I also include a library that I privately host on Bitbucket with the appropriate private keys, and install through npm. This library too is written in coffeescript.
Usually I'm able to include this library in Javascript without any headaches, using a simple require just like I would for any other library. However, occasionally one of the servers that's using the back-end gets updates, and it stops working. When I go check the error, it's always the same - 'require' passes, but instead of loading the actual library in JavaScript, it returns an empty object ({}). Running the code in coffeescript still works, but regardless of what I do - recompile, reinstall all dependencies, remove and clone the repository, the problem persists.
I've run out of ideas of what it might be myself, so I'm hoping that someone here has come across the problem before and might be able to point me in the right direction.
In the library package.json:
{
"name": "graph-engine",
"main": "./lib/graph"
}
In the library's graph.coffee
class Graph
constructor: () ->
# Perform init
module.exports = Graph
Then in the app's package.json:
{
"graph-engine": "git+ssh://git#bitbucket.org:<team>/graph-engine.git"
}
Finally, in the app itself:
GraphEngine = require "graph-engine"
engineInstance = new GraphEngine()
This works fine in coffeescript, but when compiling the app using grunt with the following setup for grunt-contrib-coffee:
coffee:
glob_to_multiple:
expand: true
flatten: false
cwd: 'src'
src: ['**/*.coffee']
dest: 'bin'
ext: '.js'
It fails to load the library correctly when running the compiled application, instead returning an empty object. Again, I'd like to emphasise that this does not always happen, and as such I didn't include any code or json files as I believed that it was unrelated.
Although the exact reason for the randomness of the behaviour eludes me to this day, I have found that it is related to these libraries being written in CoffeeScript.
It seems that depending on the load order, occasionally third party libraries would register coffee script and my own libraries would load correctly, whereas other times these libraries would load after my own libraries had loaded, resulting in an inability to load coffeescript. Therefore, the solution turned out to be fairly straightforward - register coffeescript. This can be done by putting the following at the start of the node.js app:
require('coffee-script/register')
Refer to the documentation for further information.
I am fairly new to Node.js and I want to load a few javascript files in the browser but I can't seem to find anywhere how I can simply get libraries to be loaded inside the browser.
So, my question is, how would I be able to load javascript libraries client side with Node.js?
I'm fairly new to node as well, but I've been using browserify to deal with node packages. There are a quite a few node packages that won't work in a browser - if they will work in a browser they will usually say it in their description.
Browserify is really easy to use - you just require() a module just as you would when writing a non-browser script (as far as I can tell). When you're ready to test the script on a browser, you just run
browserify input.js -o output.js
and it pulls all of the dependencies from your require()'s into output.js, so then your require()s actually reference what you want it to.
--Updated for new comment--
As I see in your answer, you are talking about node.js packages? I am
talking about standalone random javascript libraries (so, for example
just one of my own js files that I want to load client side). Can you
also load random javascript libraries with browserify? (I googled a
bit but can't figure that out)
Yeah, you can do that; although I'm afraid I can't help you with the technicalities of it (like I said, new to it myself). Here's an example:
Bar.js (my library)
module.exports = bar; //tells node what to export in this file
var bar = {
message: function(msg) {
console.log(msg)
}
}
Foo.js (my script)
var bar = require('./bar');
bar.message("foo"); //logs "foo" to console
And keep in mind that require() refers to a file. So Bar.js would need to be in the same directory as Foo.js. If Bar.js was in a different folder, you would just do require('./folder/bar'). To tie it all together, you would run browserify on Foo.js, and it would automatically grab Bar.js' contents.
There are a lot of different ways you can define exports, so you'll need to google around to see exactly how to do it for how your lib is formatted. But that's the gist of it.