How to get file link from google cloud storage using Node.js ?

To get the signed public link of a file from the firebase storage, we need a reference to the file in Google cloud storage. As we just have a path to that file in storage we would first need to create a reference to that object and then get a signed link to that file.

Steps to generate a public link to a file in storage using the file path:

1. Get the reference to the storage using a bucket() and file() methods on the storage object from @google-cloud/storage.
2. Generate a signed public link for that file using getSignedUrl method on the reference object created in the first step.

Module Installation: Install the module using the following command:

npm install @google-cloud/storage

The method getSignedUrl() tasks a config object as input and returns a Promise that resolves with the download URL or rejects if the fetch failed, including if the object did not exist.

Example: Filename: index.js 

Javascript

// Imports the Google Cloud client library
const {Storage} = require('@google-cloud/storage');

// Creates a client
const storage = new Storage();

var bucketName = 'geeksforgeeks';
var fileName = 'gfg.png';

// Create a reference to the file to generate link
var fileRef = storage.bucket(bucketName).file(fileName);

fileRef.exists().then(function(data) {
  console.log("File in database exists ");
});

const config = {
  action: 'read',

  // A timestamp when this link will expire
  expires: '01-01-2026',
};

// Get the link to that file
fileRef.getSignedUrl(config, function(err, url) {
  if (err) {
    console.error(err);
    return;
  }

  // The file is now available to
  // read from this URL
  console.log("Url is : " + url);
});

Run the index.js file using the following command:

node index.js

Output: 

File in database exists
Url is : https://storage.googleapis.com/geeksforgeeks/gfg.png?X-Goog-Algorithm=[token]

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