In the Nashorn JavaScript engine, how can I read a file from the file system? In node.js I use
fs = require('fs');
var content = fs.readFileSync("sometext.txt")
but in Nashorn this gives already an exception on the require statement.
You have two options:
1 Use the Scripting API
The Nashorn engine can be started with the -scripting flag. Once you've done this, you can use the JS function readFully to read the content of a file into a variable.
Instantiate the Nashorn engine and use it as follows (Java code):
NashornScriptEngineFactory factory = new NashornScriptEngineFactory();
ScriptEngine engine = factory.getScriptEngine(new String[] { "-scripting" });
engine.eval(new FileReader("myscript.js"));
where the JavaScript file contains:
...
var content = readFully("mytext.txt")
...
2 Use the Java API
Read the file in JavaScript via calls to the classes/functions in java.nio.file and then convert the resulting Java bytes object to JavaScript.
Instantiate the Nashorn engine in the normal manner (Java code):
ScriptEngine engine = new ScriptEngineManager().getEngineByName("Nashorn");
engine.eval(new FileReader("myscript.js"));
and put in the JavaScript file myscript.js:
var pathObj = java.nio.file.Paths.get("mytext.txt")
var bytesObj = java.nio.file.Files.readAllBytes(pathObj);
var bytes = Java.from(bytesObj) // converting to JavaScript
var content = String.fromCharCode.apply(null, bytes)
Related
Similar to How to get the arguments for opening file with electron app but the solution there is not working for me.
Using:
OS - Windows 10
Electron - https://github.com/castlabs/electron-releases.git#v1.8.7-vmp1010
electron-builde - v20.28.3
I have a an electron app build with electron-builder, and using the latter I have specified a custom file association, .custom.
So when you double-click on a file with this extension, file.custom, the installed app opens. This file would have some data in it that the app needs, and I'd like to read this data using my app.
Is there any way that my app can detect what launched it, so that I can say "file.custom" launched me, and it's sitting at "C:\Users\Owner\Downloads\,?
The file does not appear in process.argv
You can get a reference to the file using process.argv, example:
var ipc = require('ipc');
var fs = require('fs');
// read the file and send data to the render process
ipc.on('get-file-data', function(event) {
var data = null;
if (process.platform == 'win32' && process.argv.length >= 2) {
var openFilePath = process.argv[1];
data = fs.readFileSync(openFilePath, 'utf-8');
}
event.returnValue = data;
});
source: Source
https://github.com/apigee-127/swagger-converter
I see this code:
var convert = require('swagger-converter');
var fs = require('fs');
var resourceListing = JSON.parse(fs.readFileSync('/path/to/petstore/index.json').toString());
var apiDeclarations = [ JSON.parse(fs.readFileSync('/path/to/petstore/pet.json').toString()),
JSON.parse(fs.readFileSync('/path/to/petstore/user.json').toString()),
JSON.parse(fs.readFileSync('/path/to/petstore/store.json').toString())
];
var swagger2Document = convert(resourceListing, apiDeclarations);
console.log(JSON.stringify(swagger2Document, null, 2));
I'm confsued as to what exactly I'm supposed to do here to run this? Do I start a node http server?
To run the file you pasted, just save the code into a file like script.js. Then from the command line (with node installed) run node script.js. That will run the file. Here's a breakdown of what it's doing:
var convert = require('swagger-converter');
This line gets reference to the swagger-converter module that you linked to. That module is designed to allow you to convert swagger documents into JSON.
var fs = require('fs');
This line gets reference to the node built-in filesystem module (fs for short). It provides an API for interacting with the filesystem on your machine when the script is running.
var resourceListing = JSON.parse(fs.readFileSync('/path/to/petstore/index.json').toString());
This line could be broken down to:
var indexContent = fs.readFileSync('/path/to/petstore/index.json');
JSON.parse(indexContent.toString());
readFileSync returns the contents of the index.json file as a buffer object, which is easily turned into a simple string with the call to .toString(). Then they pass it to JSON.parse which parses the string and turns it into a simple JavaScript object.
Fun Fact: They could have skipped those steps with a simple var resourceListing = require('/path/to/petstore/index.json');. Node knows how to read JSON files and automatically turn them into JavaScript objects. You need only pass the path to require.
var apiDeclarations = [ JSON.parse(fs.readFileSync('/path/to/petstore/pet.json').toString()),
JSON.parse(fs.readFileSync('/path/to/petstore/user.json').toString()),
JSON.parse(fs.readFileSync('/path/to/petstore/store.json').toString())
];
This bit of code does the same thing as the resourceListing except it creates an array of three JavaScript objects based on those JSON files. They also could have used require here to save a bit of work.
Then finally they use the converter to do the conversion and then they log that data to the terminal where your script is running.
var swagger2Document = convert(resourceListing, apiDeclarations);
console.log(JSON.stringify(swagger2Document, null, 2));
JSON.stringify is the opposite of JSON.parse. stringify turns a JavaScript object into a JSON string whereas parse turns a JSON string into a JavaScript object.
Is there any module to parse javascript using node.js . I mean we are able to add and remove html content dynamically using cheerio nodejs module.
Similarly, we want to add, remove and manipulate a javascript method/variable. Is there any module to do that. I searched but unable to get one.
Thanks in Advance !!!
I would recommend the recast module. Install it via npm install --save recast. Below is a sample program that will read in the source of a module named user.js in the current directory. It will parse the source into an AST then from the AST re-generate the original source. Modify the AST with help from estraverse before you call recast.print(ast).code.
The source (does not incorporate estraverse -- exercise for the reader):
'use strict';
var recast = require('recast');
var path = require('path');
var fs = require('fs');
var file = path.resolve(__dirname, 'user.js');
var code = fs.readFileSync(file).toString();
var ast = recast.parse(code);
var output = recast.print(ast).code;
console.log(output);
I have worked a lot with rails, requirejs and backbone and know how to use haml coffee templates in rails.
App = new Backbone.Marionette.Application()
App.addInitializer (options) ->
Backbone.history.start()
alert "yay"
$ ->
alert "yay"
App.start()
How do i do it in Node.js, I have a Node.js app and i am at a deadend with regards to how do i get a template to compile client side, i am not stuck on haml coffee, any template engine will do, jade is fine too, underscore too. Just a good starting point so that i can get on with building the backbone app in node.js.
Any Help is appreciated!
I don't suggest dragging the templates to the client and compiling them there,the right way would be to use some framework such as www.socketstream.com that offers what you want and much more. If you're against frameworks quick and dirty solution to compiling them on the server and calling them as function on the client will be :
// compile.js
var fs = require("fs")
,jade = require("jade");
exports.build = function(templatesDir) {
var js = "var Templates = {}; \n\n";
var files = fs.readdirSync(templatesDir);
var jadeFiles = files.filter(function(file) {
return file.substr(-5) === ".jade";
});
for(var i = 0; i < jadeFiles.length; ++i){
var filePath, key;
var file = jadeFiles[i];
key = file.substr(0, file.indexOf("."));
filePath = templatesDir + file;
var jadeSource = fs.readFileSync(filePath);
js += "Templates." + key + " = " + jade.compile(jadeSource, {
debug: false,
client: true
}).toString() + "; \n\n";
}
return js;
};
// On the server.js
// Compile views
var viewsPath = path.join(__dirname, 'views/');
var generatedJs = require('./compile').build(viewsPath);
var savePath = path.join(__dirname, 'public/js/lib/templates.js');
fs.writeFile(savePath, generatedJs, function (err) {
if (err) throw err;
});
// Then on the client include js/lib/templates.js and use templates like this
FactSummaryView = Backbone.View.extend({
template: Templates.issueSummary,
render: function() {
this.$el.html(this.template(this.model.toJSON()));
return this;
}
});
// Also add templates.js to nodemonignore if you're using nodemon
./public/js/lib/templates.js
/public/js/lib/templates.js
You usually don't compile the templates on the client (expect the templates are edited directly in the browser), instead they are compiled in the backend and rendered in the browser.
Compile the templates
In this step you compile the template source code to a JavaScript file that contains a render function.
You can either use haml-coffee on the command line and make a script in your build process or make use of the projects listed in the integration section of the Haml-Coffee README.
Grunt is a popular solution to run certain tasks and with Grunt-Haml you have certainly a flexible build solution for your project.
Render the templates
To render the templates with Marionette you need to make sure the template render function is available on the client. Just type the configured namespace into the developer tools to see if the template functions are registered:
If this is fine, you need to have a custom template render function:
Backbone.Marionette.Renderer.render = (template, data) ->
if JST[template]
JST[template](data)
else if _.isFunction(template)
template(data)
else
console.error 'Template %s not found', template
Now you can simply define the view template and it'll be rendered properly:
class App.Views.Login extends Backbone.Marionette.ItemView
template: 'shared/_login'
I'm loading a node library in script and immediately after loading some customization that depends on that library:
var somelib = require('somelib');
// some customizations made to
// somelib's methods
require('./somelib.custom');
somelib.SomeObject = ...
^
ReferenceError: somelib is not defined
I keep getting an exception since the loading is done asynchronously and the second require happens before the first is namespaced correctly. What's a good way to resolve this? thanks.
EDIT: My original code
I'm trying to create a PNG image from json data using fabric.js node package (building on the article in package site). This is done by loading the server-side fabric canvas with JSON data that was originally generated on the client, then writing to a file stream:
var path = require('path');
var fs = require('fs');
var fabric = require('fabric').fabric;
require('./fabric.custom');
var canvas = fabric.createCanvasForNode(400, 400);
var outfile = fs.createWriteStream("image.png");
var filepath = "/path/to/file.json";
fs.readFile(filepath, 'utf8', function(err, json) {
canvas.loadFromJSON(json, function() {
var stream = canvas.createPNGStream();
stream.on('data', function(chunk) {
outfile.write(chunk);
});
});
});
The "fabric.custom" file holds several custom fabric canvas objects that override some fabric prototype defaults. They work well on the client, and are needed to properly render the canvas. It looks something like this:
fabric.TextBox = fabric.util.createClass(fabric.Text, {
type: 'text-box',
// more object specific stuff ...
});
Thanks.
Rather than relying on side effects in a require to mutate your fabric object, how about having the fabric.custom.js file export the modified fabric, like so?
fabric.custom.js:
var fabric = require('fabric').fabric;
fabric.myCustomMethod = function(){ ... }
...
module.exports = fabric; // the modified fabric
And in your main file:
var path = require('path');
var fs = require('fs');
// var fabric = require('fabric').fabric; No need for this line anymore
var modifiedFabric = require('./fabric.custom');
...
modifiedFabric.myCustomMethod( ... ); // should now be available