仅当用户在html中选择文件后，才在node.js中运行脚本

Question

I am using node.js to launch a serve so that my html can communicate with R code. But I am facing a problem on node.js. In my html page, I have a browse selection button, user can use it to choose the data file they want to read into html and node.js will pass the file name to R, so R code will read data from the selected data file and then run the analytics model. But as i only have very basic knowledge of Node.js, so currently, r code would run only when I open the followling link "localhost:3000/vis/rio". So my question is how to make node.js run the R code in background automatically when the data file has been selected. Thank you very much for your help in advance.

Here are my codes:

Javascript-(sending the file name to node.js):

var dataset,availableTags;
    function handleFileSelect(evt) {
      var file = evt.target.files[0];
      $.ajax({            //getting the file name and update to node.js
         type:'post',  
         url:"/getFileName",  
         data:{filename:file.name}
      }); 
      Papa.parse(file, {     //papa is a library I used to read csv file
        header: true,
        dynamicTyping: true,
        complete: function(results) {
        dataset=results.data;
        }
      });
    }

    $(document).ready(function(){
      $("#csv-file").change(handleFileSelect);
    });

Node.js script: serve.js:

var express=require('express');
var path = require('path');
var vis = require('./routes/vis');
var index = require('./routes/index');
var bodyParser=require('body-parser');
var app=express();
require('./routes/main')(app);
app.get('/vis/rio',vis.rio);       **//this is a package used to get connection with Rserve**
app.set('views',__dirname + '/views');
app.set('view engine', 'ejs');
app.engine('html', require('ejs').renderFile);
app.use(express.static(path.join(__dirname, 'public')));
app.use(bodyParser.urlencoded());              
app.post("/getFileName",index.getFileName);    **//this is the script to get the file name, it is from index.js** 
var server=app.listen(3000,function(){
console.log("Express is running on port 3000");
});

index.js // this is the js file for getting file name

var express = require('express');
var router = express.Router();

/* GET home page. */
router.get('/', function(req, res) {
  res.render('index', { title: 'Express' });
});

getFileName=function (req,res){
    global.filename=req.body.filename; **//this is the global variable which stores the file name**
    res.send('true');
};

module.exports = {router:router,getFileName:getFileName};

vis.js // this is the file used to connect with Rserve and pass the name to R code

var rio = require("rio");
var arg={};

exports.rio = function(req, res){
    arg={names:[global.filename]};
    console.log(arg);
     options = {
        entryPoint:"nameoffile",
        data: arg,
        host : "127.0.0.1",
        port : 6311,
        callback: function (err, val) {
            if (!err) {
                 console.log("RETURN:"+val);
                 return res.send({'success':true,'res':val});
            } else {
                 console.log("ERROR:Rserve call failed")
                 return res.send({'success':false});
            }
        },
    }
    rio.enableDebug(true);
    rio.sourceAndEval(__dirname + "/Rcode/test.R",options);
};

Answer 1

It looks like you aren't calling out to /vis/rio at any point when you make the call out to your server.

You'll either need to make a second call on the client side to /vis/rio or if you want to use that section, you can import/require the module in index.js and include it in getFileName and just call out to the function there before you return the file. I'm not super familiar with rio, but I don't see any access point in your code to that function.

Edit: If I understand what you're trying to do correctly, you can always make a second request (to /vis/rio) in the success callback of your first ajax call.