fs.write json file to capture and save streaming json file - javascript

I want json stream stored in text file. When running the node server, the json file isn't appended to the json.txt file. What am I missing? Am new to to node, so be gentle..
Here is a code chunk I expect to capture the json content:
var fs = require('fs');
fs.writeFile("json.txt",{encoding:"utf8"}, function(err) {
if(err) {
console.log(err);
} else {
console.log("The file was saved!");
}
});

The issue is you aren't using the correct parameters. When calling fs.writeFile it expects a string for the filename, a buffer or string for the content, an object for the options and a callback function. What it looks like you're doing is sending the options as the second parameter when it expects a buffer or a string. Correction below;
var fs = require('fs');
fs.writeFile("json.txt", JSON.stringify({some: object}), {encoding:"utf8"}, function(err) {
if(err) {
console.log(err);
} else {
console.log("The file was saved!");
}
});
You can replace the JSON.stringify part with some plain text if you wanted to, but you specified JSON in your question so I assumed you wanted to store some object in a file
Source (NodeJS documentation)
EDIT:
The links to other questions in the comments may be more relevant if you want to add new lines to the end of the file and not completely overwrite the old one. However I made the assumption that fs.writeFile was the intended function. If that wasn't the intention, those other questions will help a lot more
UPDATE:
It seems the issue was the fact that the body wasn't being parsed, so when the POST request was going through, Node didn't have the request body. To alleviate this, during the express configuration, the following code is needed:
var bodyParser = require('body-parser');
app.use(bodyParser.json());
Uses the npm module body-parser. This will convert the JSON body to a JavaScript object, and it is accessible via req.body.

Related

Create File object without saving

I'm trying to look for a way to create a .txt File object without saving it to disk in Node.js. In browser I'd do something like
new File(['file_contents'], 'file_name.txt', {type: 'text/plain'})
The end aim is to create a .txt file object temporarily for my Discord Bot to send as a message attachment.
From the discord.js documentation, I presume I'm supposed to create a Buffer or Stream object representing the file.
I'm already using require('node-fetch') library to read attachments in messages, if that has any relevancy (but can't see anything in their docs on this either).
After playing around in console I've found Buffer.from('string of txt file contents') to represent the file seems to work fine.
Usage:
channel.send(new Discord.MessageAttachment(Buffer.from('Hello World'), 'file_name.txt'))
In order to write a text file in JS you should use the fs library, included in Node.js.
Here is an example of writing to a file:
fs = require('fs');
let content = "Hello world!";
fs.writeFile('file.txt', content, function (err) {
if (err) return console.log(err);
// Code here will execute if successfully written
});
Then in order to send a local file to Discord you can use .send with an object containing a files property in it, like this:
channel.send({
files: [{
attachment: 'entire/path/to/file.txt',
name: 'file.txt'
}]
}).then(() => {
// Delete file
fs.unlink('file.txt');
});
You can see more about .send() here and you can find more about the fs module here

How to download a file in the browser directly from the node.js server side without any variable?

My app is created with mean and I am a user of docker too. The purpose of my app is to create and download a CSV file. I already created my file, compressed it and placed it in a temp folder (the file will be removed after the download). This part is in the nodejs server side and works without problems.
I already use several things like (res.download) which is supposed to download directly the file in the browser but nothing append. I tried to use blob in the angularjs part but it doesn't work.
The getData function creates and compresses the file (it exists I can reach it directly when I look where the app is saved).
exports.getData = function getData(req, res, next){
var listRequest = req.body.params.listURL;
var stringTags = req.body.params.tagString;
//The name of the compressed CSV file
var nameFile = req.body.params.fileName;
var query = url.parse(req.url, true).query;
//The function which create the file
ApollineData.getData(listRequest, stringTags, nameFile)
.then(function (response){
var filePath = '/opt/mean.js/modules/apolline/client/CSVDownload/'+response;
const file = fs.createReadStream(filePath);
res.download(filePath, response);
})
.catch(function (response){
console.log(response);
});
};
My main problem is to download this file directly in the browser without using any variable because it could be huge (like several GB). I want to download it and then delete it.
There is nothing wrong with res.download
Probably the reason why res.download don't work for you is b/c you are using AJAX to fetch the resource, Do a regular navigation. Or if it requires some post data and another method: create a form and submit.

Is there a way to download any kind of file using angular filesaver?

I'm using node.js and angular.js for my app and I'm trying to download files through the browser using Blob and fileSaver.js.
I've used these in other sections of my app to download text files and pdf files specifying the correct type when creating the Blob object without any problem, but in the current section I need to support any type of file and I don't know if it's possible.
For example, I've tried downloading an image file with and without type:image/png and the result was a corrupted image - inspecting it in a text editor and comparing it with the original file shows that many of the bytes were changed.
Here are the code snippets I use:
Server:
fs.readFile(/* snipped file path */, function(err, data){
if(err){
/* handle error */
}
else{
res.send(data);
}
});
Client:
$http.get(/* endPoint URL */)
.success(function(result){
var data = new Blob([result], {type: 'image/png'});
FileSaver.saveAs(data, filename);
});
A few questions:
Do I need to specify type for Blob? If so, do I need to specify it at server, too (it's a pain to determine it)? Can't I just skip it on both ends?
What causes the image test to result in corrupted file? Am I missing some content-type header or something?
Try adding {contentType: 'arraybuffer'} to your GET request and remove type from Blob definition, like so:
$http.get(/* endPoint URL */, {contentType: 'arraybuffer'})
.success(function(result){
var data = new Blob([result]);
FileSaver.saveAs(data, filename);
});
(Edit: deleted redundant type definition from Blob)

How to edit File in perfoce with node js?

If i have the code below how can i edit the specific file and make the right corrections?
var p4 = require('C:/Program Files/nodejs/node_modules/p4');
var File = process.argv[2];
p4.edit(File, function(err, data) {
if (err) {
console.error(err.message);
}
console.log(data);
});
Your code looks correct to open the file for edit. If that returns any errors when you run it, you should post those here, but I'll assume that it returns a success message ("(file) opened for edit").
Opening the file for edit means that it is made writable on the local filesystem (i.e. the one where this code is running -- the file is the one you passed as an argument to the edit command). To actually modify the file you can use any other function at your disposal.

Parse json object when node server is started

I need to parse json object when the node server.js(which is my entry point to the program) is started ,the parse of the json file is done in diffrent module in my project.
I've two questions
Is it recommended to invoke the parse function with event in the server.js file
I read about the event.emiter but not sure how to invoke function
from different module...example will be very helpful
I've multiple JSON files
UPDATE to make it more clear
if I read 3 json file object (50 lines each) when the server/app is loaded (server.js file) this will be fast I guess. my scenario is that the list of the valid path's for the express call is in this json files
app.get('/run1', function (req, res) {
res.send('Hello World!');
});
So run1 should be defined in the json file(like white list of path's) if user put run2 which I not defined I need to provide error so I think that when the server is up to do this call and keep this obj with all config valid path and when user make a call just get this object which alreay parsed (when the server loaded ) and verify if its OK, I think its better approach instead doing this on call
UPDATE 2
I'll try explain more simple.
Lets assume that you have white list of path which you should listen,
like run1
app.get('/run1', function
Those path list are defined in jsons files inside your project under specific folder,before every call to your application via express you should verify that this path that was requested is in the path list of json. this is given. now how to do it.
Currently I've develop module which seek the json files in this and find if specific path is exist there.
Now I think that right solution is that when the node application is started to invoke this functionality and keep the list of valid paths in some object which I can access very easy during the user call and check if path there.
my question is how to provide some event to the validator module when the node app(Server.js) is up to provide this object.
If it's a part of your application initialization, then you could read and parse this JSON file synchronously, using either fs.readFileSync and JSON.parse, or require:
var config = require('path/to/my/config.json');
Just make sure that the module handling this JSON loading is required in your application root before app.listen call.
In this case JSON data will be loaded and parsed by the time you server will start, and there will be no need to trouble yourself with callbacks or event emitters.
I can't see any benefits of loading your initial config asynchronously for two reasons:
The bottleneck of JSON parsing is the parser itself, but since it's synchronous, you won't gain anything here. So, the only part you'll be able to optimize is interactions with your file system (i.e. reading data from disk).
Your application won't be able to work properly until this data will be loaded.
Update
If for some reason you can't make your initialization synchronous, you could delay starting your application until initialization is done.
The easiest solution here is to move app.listen part inside of initialization callback:
// initialization.js
var glob = require('glob')
var path = require('path')
module.exports = function initialization (done) {
var data = {}
glob('./config/*.json', function (err, files) {
if (err) throw err
files.forEach(function (file) {
var filename = path.basename(file)
data[filename] = require(file)
})
done(data);
})
}
// server.js
var initialization = require('./initialization')
var app = require('express')()
initialization(function (data) {
app.use(require('./my-middleware')(data))
app.listen(8000)
})
An alternative solution is to use simple event emitter to signal that your data is ready:
// config.js
var glob = require('glob')
var path = require('path')
var events = require('events')
var obj = new events.EventEmitter()
obj.data = {}
glob('./config/*.json', function (err, files) {
if (err) throw err
files.forEach(function (file) {
var filename = path.basename(file)
obj.data[filename] = require(file)
})
obj.emit('ready')
})
module.exports = obj
// server.js
var config = require('./config')
var app = require('express')()
app.use(require('./my-middleware'))
config.on('ready', function () {
app.listen(8000)
})

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