通过从Node.js和Express.js中的前端请求数据来创建动态链接

Question

This is kind of hard for me to explain but I am trying to shorten my code by creating one link instead of 50 for downloading a form. I will try to explain this a bit better using my code.

I have 5 get requests that do exactly the same thing but download a different file.

router.get('/form1', function (req, res) {
    var file = __dirname + '/../public/forms/form1.pdf';
    res.download(file);
});

router.get('/form2', function (req, res) {
    var file = __dirname + '/../public/forms/form2.pdf';
    res.download(file); 
});
etc...

and my front-end link are;

<a href="/downloads/form1">FORM 1</a>
<a href="/downloads/form2">FORM 2</a>
etc...

Is there anything I can do to make this a more dynamic? The only way I can think of is something like this;

router.get('/:formName', function (req, res) {
    // some how do a "req.params.formName" 
    var file = __dirname + '/../public/forms/' + req.params.formName + '.pdf';
    res.download(file); // Set disposition and send it.
});

But I don't know how I will get the formName or if thats even possible.

Answer 1

This response assumes that your route lives in index.js .

router.get('/form/:formName', (req, res, next) => {
  res.download(`${__dirname}/../public/forms/${req.params.formName}.pdf`);
});

<a href="/form/form2">FORM 2</a>

Be careful about your path. I don't know whether you can start at a directory, go up a level, then down again.

Answer 2

Here are some more options to clarify:

• Option 1: If you have a folder on the server with a fairly manageable directory structure, simply use express.static to map the physical folder to a virtual one with automatic download:

   app.use('/download', express.static(path.join(__dirname, '/public/forms/'))) 

  This will result in any link from the front-end with href='/download/something.pdf' working as long as that file is on the server in the path you mapped (ie in /public/forms).

• Option 2 (which David E above answered in essence): In your original code, if you wanted to generate a path handler for a link that looks like /download/form1, /download/form2, it's a very minor modification:

   router.get('/download/:formNumber', function (req, res) { var file = __dirname + '/public/forms/' + req.params.formNumber + '.pdf'; res.download(file); }); 

• Option 3: You want to authenticate access to the files and potentially support multiple, complex URL schemes to a single handler that can lookup the appropriate physical path and send the file:

   router.get('/download/:path[forms|images|files]/:formNumber1', fileRequestHandler); router.get('/public/downloadFolder2/:formNumber2', fileRequestHandler); router.get('/public/downloadFolder3/:formNumber3', fileRequestHandler); function fileRequestHandler(req, res) { // Check authentication here - example below from Passport if(!req.isAuthenticated()) return res.status(401).send({err: 'Unauthorized'}); // Check which form number is supplied and map to appropriate physical file if(req.params.formNumber1) { // in this example, req.params.path can be one of three allowed sample values - forms or images or files var file = __dirname + '/public/' + req.params.path + '/' + req.params.formNumber + '.pdf'; res.download(file); } else if(req.params.formNumber2) { // etc. } } 

Note: Ezra Chang's point about path validity is important.