(Node.js) Download Object from Google Cloud Storage

Demonstrates how to download an object from Google Cloud Storage to a file.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // This example uses a previously obtained access token having permission for the 
    // scope "https://www.googleapis.com/auth/cloud-platform"

    // In this example, Get Google Cloud Storage OAuth2 Access Token, 
    // the service account access token was saved to a text file.  This example fetches the access token from the file..
    var sbToken = new chilkat.StringBuilder();
    sbToken.LoadFile("qa_data/tokens/googleCloudStorageAccessToken.txt","utf-8");

    // Send a GET equivalent to this curl command.

    // curl -X GET \
    //     -H "Authorization: Bearer [OAUTH2_TOKEN]" \
    //     -o "[SAVE_TO_LOCATION]" \
    //     "https://www.googleapis.com/storage/v1/b/[BUCKET_NAME]/o/[OBJECT_NAME]?alt=media"

    var http = new chilkat.Http();

    http.AuthToken = sbToken.GetAsString();

    // Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
    http.SetUrlVar("bucket_name","chilkat-ocean");
    http.SetUrlVar("object_name","starfish.jpg");
    var url = "https://www.googleapis.com/storage/v1/b/{$bucket_name}/o/{$object_name}?alt=media";

    // If there is an error response, then we didn't actually download the file data,
    // but instead we downloaded an error response..
    var fileData = new chilkat.BinData();
    var success = http.DownloadBd(url,fileData);
    if (success == false) {
        console.log(http.LastErrorText);
        return;
    }

    var sbErrorResponse = new chilkat.StringBuilder();
    var responseCode = http.LastStatus;
    if (responseCode == 401) {
        console.log("If invalid credentials, then it is likely the access token expired.");
        console.log("Your app should automatically fetch a new access token and re-try.");
    }

    if (responseCode !== 200) {
        // Get the error response
        sbErrorResponse.AppendBd(fileData,"utf-8",0,0);
        console.log("Error response code = " + responseCode);
        console.log("Error:");
        console.log(sbErrorResponse.GetAsString());
        return;
    }

    console.log("Success.");

    // Save the downloaded data to a file.
    success = fileData.WriteFile("qa_output/starfish.jpg");

}

chilkatExample();