javascript - Why won't my file download with nodejs? -

i send xmlhttprequest webpage nodejs router so:

var name = $(this).find('td:eq(0)').html();         var docnum = $('#docnum').val();         //alert("filename=" + name + "&docnum=" + docnum);         xhttp = new xmlhttprequest();         xhttp.onreadystatechange = function() {             if (xhttp.readystate == 4 && xhttp.status == 200) {                 isunique = xhttp.responsetext;                 if(isunique == "false"){                     alert("id not unique please pick document id ");                 }else{                     $("form#docform").submit();                 }             }         };         xhttp.open("post", "/downloaddocument", true);         xhttp.setrequestheader("content-type", "application/x-www-form-urlencoded");         var params = "filename=" + name + "&docnum=" + docnum;         xhttp.send(params); 

and works fine, request gets router , router able read both variables properly.

this part of router code doesn't work properly:

router.post("/downloaddocument", function(req, res){         var doc = req.body.docnum;         var filename = req.body.filename;         var document = document.findone({name: filename, dossier: doc}, function(err, obj){             var path = obj.name;             console.log(path);             fs.writefile(obj.name, obj.file);             res.download("./" + obj.name);         });     }); 

and redirect me previous page, doesn't download file, though file exists, , have no idea why.

i've tried using

  var filestream = fs.createreadstream(obj.file);   filestream.pipe(res);  

instead of res.download

here console output request:

apples.jpg post /downloaddocument 200 4.814 ms - - post /dossieredit 302 12.898 ms - 62 #this part concerns me , redirects me while not ask page in code /dossiers 304 20.793 ms - - /public/stylesheets/css/bootstrap.min.css 304 2.737 ms - - /public/stylesheets/css/simple-sidebar.css 304 2.921 ms - - /public/stylesheets/style.css 304 2.327 ms - - /public/stylesheets/css/font-awesome.min.css 404 3.502 ms - 56 /public/css/style.css 404 1.097 ms - 33 /public/stylesheets/css/font-awesome.min.css 404 0.492 ms - 56 /public/css/style.css 404 1.107 ms - 33 

just clarify, goal have file sent client, not saved server.

i believe there couple of issues.

1. files cannot downloaded via ajax call.
2. the fs.writefile(obj.name, obj.file) call asynchronous, if (1) wasn't issue, file not present when res.download("./" + obj.name) called. use fs.writefilesync instead.
3. you getting redirected previous page because of $("form#docform").submit() call happens when ajax call returns, submits form other page.

to resolve issue, try submitting actual form post data "/downloaddocument" endpoint instead of doing ajax call.

i hope helps.