Express.js res.download() Function

The res.download() function transfers the file at path as an ‘attachment’. Typically, browsers will prompt the user to download.

Syntax:

res.download(path [, filename] [, options] [, fn])

Parameters: The filename is the name of the file which is to be downloaded as attachment and fn is a callback function.

Return Value: It does not return anything.

Installation of express module:



  1. You can visit the link to Install express module. You can install this package by using this command.
    npm install express
  2. After installing the express module, you can check your express version in command prompt using the command.
    npm version express
  3. After that, you can just create a folder and add a file for example, index.js. To run this file you need to run the following command.
    node index.js

Example 1: Filename: index.js

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var express = require('express');
var app = express();
var PORT = 3000;
  
app.get('/', function(req, res){
    res.download('Hello.txt');
});
  
app.listen(PORT, function(err){
    if (err) console.log(err);
    console.log("Server listening on PORT", PORT);
});

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Place any file in root directory of the project which can be downloaded, like here we have used Hello.txt.

Steps to run the program:

  1. Make sure you have installed express module using the following command:
    npm install express
  2. Run index.js file using below command:
    node index.js

    Output:

    Server listening on PORT 3000
    
  3. Open your browser and go to http://localhost:3000/, now you can see the “Hello.txt” file being downloaded on your screen.

Example 2: Filename: index.js

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var express = require('express');
var app = express();
var PORT = 3000;
   
app.get('/', function(req, res){
    res.download('Unknown_file.txt', function(error){
        console.log("Error : ", error)
    });
});
   
app.listen(PORT, function(err){
    if (err) console.log(err);
    console.log("Server listening on PORT", PORT);
});

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Run index.js file using below command:

node index.js

Open your browser and go to http://localhost:3000/, then you will see the following output on your console:

Error :  [Error: ENOENT: no such file or directory, 
  stat 'C:\\Users\\Unknown_file.txt'] {
  errno: -4058,
  code: 'ENOENT',
  syscall: 'stat',
  path: 'C:\\Users\\Unknown_file.txt',
  expose: false,
  statusCode: 404,
  status: 404
}

Reference: https://expressjs.com/en/4x/api.html#res.download




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