I have an API which uses Node.js + Express on the backend.
For one of the API endpoints, I'd like to use the Express response object method of "sendFile", documented here:
https://expressjs.com/en/api.html#res.sendFile
The API should return a Javascript file through the sendFile method.
What I can't figure out is how to read in the .js file on the front end so that I can use the JavaScript functions defined in the file. The sendFile portion appears to be working -- it's just the use of the file which I can't figure out.
Here's what I'm doing on the backend:
app.get("/api/member", async (req, res) => {
options = {
root: path.join(__dirname, '/static'),
dotfiles: 'deny'
}
res.sendFile("member.js", options, (err) => {
if (err) {
console.log(err)
next(err)
} else {
console.log('Sent file')
}
})
});
This seems to be working fine, as I can navigate to the endpoint on my localhost and it loads the JS file. The file member.js simply contains some javascript function definitions.
But, I can't figure out how to consume/use the file once it arrives to the front end.
Here's what I have currently on the frontend:
async function refreshJS() {
const url = `${baseUrl}/member`;
const response = await fetch(url, { credentials: "include" });
const script = document.createElement("script")
script.type = "text/javascript"
script.src = response.body
document.head.appendChild(script)
eval(script)
}
I've spent a lot of time looking through the console/debugger to find the text associated with the JS functions -- but they're nowhere to be found.
I've tested this general framework by loading JS files locally through the console and it worked, so I think it's wrapped up in a misunderstanding of where the JS functions live in the API response. For example, if I replace the command above of:
script.src = response.body
with
script.src = "member.js"
then everything works fine provided I have the file locally.
The examples that I've reviewed seem to deal exclusively with sending an HTML file which is loaded on the frontend. But, I can't find supporting documentation from the fetch API to understand how to use the JS file contents.
Related
I'm coding for an API connection area, that's predominately graphql but needs to have some REST connections for certain things, and have equivalent to the following code:
foo.js
module.exports = {
routes: () => {
return [
{
method: 'GET',
path: '/existing_endpoint',
handler: module.exports.existing_endpoint
},
{
method: 'POST',
path: '/new_endpoint',
handler: module.exports.new_endpoint // <--- this not passing variables
}
]
},
existing_endpoint: async () => {
/* endpoint that isn't the concern of this */
},
new_endpoint: async (req, res) => {
console.log({req, res})
return 1
}
}
The existing GET endpoint works fine, but my POST endpoint always errors out with the console of {} where {req, res} should have been passed in by the router, I suspect because the POST isn't receiving. I've tried changing the POST declaration in the routes to module.exports.new_endpoint(req, res), but it tells me the variables aren't found, and the lead-in server.js does have the file (it looks more like this...), and doing similar with the server.js, also getting similar results, implying that's probably wrong too. Also, we have a really strict eslint setup, so I can't really change the format of the call.
Every example I've seen online using these libraries is some short form, or includes the function in the routes call, and isn't some long form like this. How do I do a POST in this format?
/* hapi, environment variables, apollog server, log engine, etc. */
/* preceeding library inclusions */
const foo = require('./routes/foo')
const other_route = require('./routes/other_route')
const startServer = async () => {
const server = Hapi.server({port, host})
server.route(other_route.routes())
server.route(foo.routes())
}
This is a bug with Hapi in node v16. I just opened an issue.
Your current solutions are either:
Upgrade to Hapi v20
Use n or another method to downgrade to node v14.16 for this project. I can confirm that POST requests do not hang in this version.
I am trying to generate a rss.xml file for my angular 8 app with ssr + firebase + gcp inside the domain.
I've created a RssComponent which can be reached at /rss route. There i call getNews() method and receive an array of objects. Then I make a http request to /api/rss and in server.ts i handle that request:
app.post('/api/rss', (req, res) => {
const data = req.body.data;
const feedOptions = // defining options here
const feed = new RSS(feedOptions);
data.forEach((item) => {
feed.item({
title: item.headingUa,
description: item.data[0].dataUa,
url: item.rssLink,
guid: item.id,
date: item.utcDate,
enclosure: {url: item.mainImg.url.toString().replace('&', '&'), type: 'image/jpeg'}
});
});
const xml = feed.xml({indent: true});
fs.chmod('dist/browser/rss.xml', 0o600, () => {
fs.writeFile('dist/browser/rss.xml', xml, 'utf8', function() {
res.status(200).end();
});
});
});
And finally on response i'm opening the recently generated rss.xml file in RssComponent. Locally everything is working fine but on Google Cloud Platform it's not generating a file.
As explained in the Cloud Functions docs:
The only writeable part of the filesystem is the /tmp directory
Try changing the path to the file to the /tmp directory.
Nevertheless, using local files in a serverless environment is a really bad idea. You should assume the instance handling the following request will not be the same as the previous one.
The best way to handle this would be to avoid writing local files and instead storing the generated file in GCP Storage or Firebase Storage, and then retrieving it from there when needed.
This will ensure your functions are idempotent, and also will comply with the best practices.
I am new to Node, and I am trying to make it so that when I go to 'localhost:1337/download/open' it renders a webpage, as well as download a file.. I understand that you can only set a header once (that is the error I am getting), but what is the easiest way to both render html AND download a file? Code below:
const express = require('express');
const app = express();
app.get('/download/open', function (req, res) {
let file = `${__dirname}/downloads/Open Tasks.csv`;
res.download(file);
res.send("words");
})
app.listen(1337, function (err) {
if (err) {
console.log(err)
return
}
console.log(`App running. listening on: http://localhost:1337`);
});
Error:
Error: Can't set headers after they are sent.
Thank you in advance.
I was able to figure out what I was trying to do. Instead of trying to render a whole new page AND download a file, I needed to dedicate a route to just a download through the use of an <a></a> tag.
For instance, if I have a webpage at 'http://localhost:1337' that has a link on it like:
Download Open Tasks
Download Open Tasks
Then in node.js I have a route for 'download/open' like so:
app.get('/download/open', function (req, res) {
let file = `${__dirname}/downloads/Open Tasks.csv`;
res.download(file);
})
It will not open a new page (like I thought it needed to) it will just download the file.
IMO, I would suggest you should do the following to achieve your goal:
render the HTML result for "GET http://localhost:1337/download/open"
In the HTML file /download/open, put AJAX block to invoke download file operation
(Download a file by jQuery.Ajax)
$(document).ready(function(){
//code to invoke download file....
});
In our application we store our reports in a user defined folders. User can add their own folders during runtime. Iam showing the history of those files in a web page. on clicking the file name i should show the file from the folder. How can i show the files from a non public directory.Since its given during runtime i havent added them as static dir to the express server.
One idea we tried was to use node-static-server and create a file server with the folder and serve the file. for each file we create this. it works fine but i get an error saying "port already in use". is there any better idea to do this? is this the right approach?
You can do this in NodeJS using a express.static:
const FS = require('fs')
const express = require('express')
const bp = require('body-parser')
const app = express()
function fileTest(req, res, next){
if (/\.|\/|\\/.test(req.params.file))
return res.sendStatus(400)
return next();
}
app.get(
'/static/:file',
fileTest,
function(req, res, next){
req.url = req.url.replace('/static','')
next()
},
express.static(
'./static',
{
fallthrough: false
}
)
)
app.post(
'/static/:file',
fileTest,
bp.text(),
function (req, res) {
FS.writeFile(
'./static/'+req.params.file,
req.body,
function (err) {
if(err)
return res.sendStatus(500)
return res.sendStatus(200)
}
)
}
)
app.listen(
1337
)
This is a simple example showing a server that will:
[POST]
Take a text body and load it into memory( pitfall: large bodies in memory )
Based on the URL, save it as a file in the static folder
[GET]
Search for a file
If found return file
The good news is that you can make the file and then request the file without restarting the server. Bad news is that this is a VERY SLOW server( comparatively to other options ).
As with all examples no good practices were followed, so be sure to adapt it to your needs.
Things to think about as you adopt it:
How do I allow people to save files to other folders?
How do I disallow people from saving files to other folders I don't want them to?
PROPER AUTHORIZATION
I'm facing a strange behaviour with PdfKit. I'm using Nodejs and Express. When I call my route that generate the PDF, the route itself is called twice, and I don't understand why.
Below is the smallest code that recreate this:
var express = require('express'),
app = express();
app.get('/', function (req, res) {
console.log('Route called with referer', req.headers.referer);
var PdfDocument = require('pdfkit'),
doc = new PdfDocument();
doc.pipe(res);
doc.addPage();
doc.end();
});
app.listen(7373, function () {
console.log('started');
});
In the terminal, I have these logs, refreshing only one time the page from the browser:
node tmp/server.js
started
Route called with referer undefined
Route called with referer http://127.0.0.1:7373/
Anyone knows why the route is called one more time automatically?
Ok, after some analysis, I found that it's the browser's PDF viewer that launch a second call. When using wget or curl, I see only one call and one log. So just be aware that code is parsed twice when diplaying the page from the browser.