---

name: cloud-storage-web description: Complete guide for CloudBase cloud storage using Web SDK (@cloudbase/js-sdk) - upload, download, temporary URLs, file management, and best practices. alwaysApply: false

Cloud Storage Web SDK

Use this skill when building web applications that need to upload, download, or manage files using CloudBase cloud storage via the @cloudbase/js-sdk (Web SDK).

When to use this skill

Use this skill for file storage operations in web applications when you need to:

• Upload files from web browsers to CloudBase cloud storage
• Generate temporary download URLs for stored files
• Delete files from cloud storage
• Download files from cloud storage to local browser

Do NOT use for:

• Mini-program file operations (use mini-program specific skills)
• Backend file operations (use Node SDK skills)
• Database operations (use database skills)

How to use this skill (for a coding agent)

1. Initialize CloudBase SDK

   • Ask the user for their CloudBase environment ID
   • Always use the standard initialization pattern shown below

2. Choose the right storage method

   • uploadFile - For uploading files from browser to cloud storage
   • getTempFileURL - For generating temporary download links
   • deleteFile - For deleting files from storage
   • downloadFile - For downloading files to browser

3. Handle CORS requirements

   • Remind users to add their domain to CloudBase console security domains
   • This prevents CORS errors during file operations

4. Follow file path rules

   • Use valid characters: [0-9a-zA-Z], /, !, -, _, ., , *, Chinese characters
   • Use / for folder structure (e.g., folder/file.jpg)

---

SDK Initialization

import cloudbase from "@cloudbase/js-sdk";

const app = cloudbase.init({
  env: "your-env-id", // Replace with your CloudBase environment ID
});

Initialization rules:

• Always use synchronous initialization with the pattern above
• Do not lazy-load the SDK with dynamic imports
• Keep a single shared app instance across your application

File Upload (uploadFile)

Basic Usage

const result = await app.uploadFile({
  cloudPath: "folder/filename.jpg", // File path in cloud storage
  filePath: fileInput.files[0],     // HTML file input element
});

// Result contains:
{
  fileID: "cloud://env-id/folder/filename.jpg", // Unique file identifier
  // ... other metadata
}

Advanced Upload with Progress

const result = await app.uploadFile({
  cloudPath: "uploads/avatar.jpg",
  filePath: selectedFile,
  method: "put", // "post" or "put" (default: "put")
  onUploadProgress: (progressEvent) => {
    const percent = Math.round(
      (progressEvent.loaded * 100) / progressEvent.total
    );
    console.log(`Upload progress: ${percent}%`);
    // Update UI progress bar here
  }
});

Parameters

Parameter	Type	Required	Description
cloudPath	string	Yes	Absolute path with filename (e.g., "folder/file.jpg")
filePath	File	Yes	HTML file input object
method	"post" | "put"	No	Upload method (default: "put")
onUploadProgress	function	No	Progress callback function

Cloud Path Rules

• Valid characters: [0-9a-zA-Z], /, !, -, _, ., , *, Chinese characters
• Invalid characters: Other special characters
• Structure: Use / to create folder hierarchy
• Examples:
  • "avatar.jpg"
  • "uploads/avatar.jpg"
  • "user/123/avatar.jpg"

CORS Configuration

⚠️ IMPORTANT: To prevent CORS errors, add your domain to CloudBase console:

1. Go to CloudBase Console → Environment → Security Sources → Security Domains
2. Add your frontend domain (e.g., https://your-app.com, http://localhost:3000)
3. If CORS errors occur, remove and re-add the domain

Temporary Download URLs (getTempFileURL)

Basic Usage

const result = await app.getTempFileURL({
  fileList: [
    {
      fileID: "cloud://env-id/folder/filename.jpg",
      maxAge: 3600 // URL valid for 1 hour (seconds)
    }
  ]
});

// Access the download URL
result.fileList.forEach(file => {
  if (file.code === "SUCCESS") {
    console.log("Download URL:", file.tempFileURL);
    // Use this URL to download or display the file
  }
});

Multiple Files

const result = await app.getTempFileURL({
  fileList: [
    {
      fileID: "cloud://env-id/image1.jpg",
      maxAge: 7200 // 2 hours
    },
    {
      fileID: "cloud://env-id/document.pdf",
      maxAge: 86400 // 24 hours
    }
  ]
});

Parameters

Parameter	Type	Required	Description
fileList	Array	Yes	Array of file objects

fileList Item Structure

Parameter	Type	Required	Description
fileID	string	Yes	Cloud storage file ID
maxAge	number	Yes	URL validity period in seconds

Response Structure

{
  code: "SUCCESS",
  fileList: [
    {
      code: "SUCCESS",
      fileID: "cloud://env-id/folder/filename.jpg",
      tempFileURL: "https://temporary-download-url"
    }
  ]
}

Best Practices

• Set appropriate maxAge based on use case (1 hour to 24 hours)
• Handle SUCCESS/ERROR codes in response
• Use temporary URLs for private file access
• Cache URLs if needed, but respect expiration time

File Deletion (deleteFile)

Basic Usage

const result = await app.deleteFile({
  fileList: [
    "cloud://env-id/folder/filename.jpg"
  ]
});

// Check deletion results
result.fileList.forEach(file => {
  if (file.code === "SUCCESS") {
    console.log("File deleted:", file.fileID);
  } else {
    console.error("Failed to delete:", file.fileID);
  }
});

Multiple Files

const result = await app.deleteFile({
  fileList: [
    "cloud://env-id/old-avatar.jpg",
    "cloud://env-id/temp-upload.jpg",
    "cloud://env-id/cache-file.dat"
  ]
});

Parameters

Parameter	Type	Required	Description
fileList	Array	Yes	Array of file IDs to delete

Response Structure

{
  fileList: [
    {
      code: "SUCCESS",
      fileID: "cloud://env-id/folder/filename.jpg"
    }
  ]
}

Best Practices

• Always check response codes before assuming deletion success
• Use this for cleanup operations (old avatars, temp files, etc.)
• Consider batching multiple deletions for efficiency

File Download (downloadFile)

Basic Usage

const result = await app.downloadFile({
  fileID: "cloud://env-id/folder/filename.jpg"
});

// File is downloaded to browser default download location

Parameters

Parameter	Type	Required	Description
fileID	string	Yes	Cloud storage file ID

Response Structure

{
  // Success response (no specific data returned)
  // File is downloaded to browser
}

Best Practices

• Use for user-initiated downloads (save file dialogs)
• For programmatic file access, use getTempFileURL instead
• Handle download errors appropriately

Error Handling

All storage operations should include proper error handling:

try {
  const result = await app.uploadFile({
    cloudPath: "uploads/file.jpg",
    filePath: selectedFile
  });

  if (result.code) {
    // Handle error
    console.error("Upload failed:", result.message);
  } else {
    // Success
    console.log("File uploaded:", result.fileID);
  }
} catch (error) {
  console.error("Storage operation failed:", error);
}

Common Error Codes

• INVALID_PARAM - Invalid parameters
• PERMISSION_DENIED - Insufficient permissions
• RESOURCE_NOT_FOUND - File not found
• SYS_ERR - System error

Best Practices

1. File Organization: Use consistent folder structures (uploads/, avatars/, documents/)
2. Naming Conventions: Use descriptive filenames with timestamps if needed
3. Progress Feedback: Show upload progress for better UX
4. Cleanup: Delete temporary/unused files to save storage costs
5. Security: Validate file types and sizes before upload
6. Caching: Cache download URLs appropriately but respect expiration
7. Batch Operations: Use arrays for multiple file operations when possible

Performance Considerations

1. File Size Limits: Be aware of CloudBase file size limits
2. Concurrent Uploads: Limit concurrent uploads to prevent browser overload
3. Progress Monitoring: Use progress callbacks for large file uploads
4. Temporary URLs: Generate URLs only when needed, with appropriate expiration

Security Considerations

1. Domain Whitelisting: Always configure security domains to prevent CORS issues
2. Access Control: Use appropriate file permissions (public vs private)
3. URL Expiration: Set reasonable expiration times for temporary URLs
4. User Permissions: Ensure users can only access their own files when appropriate