Storage and functions 

We can trigger a cloud function in response to uploading, downloading or deleting files and folders in a storage bucket. To trigger a function for storage changes, developers can make use of functions.storage to create a function that handles storage events. Based on the use case, we can trigger cloud functions to a specific bucket or to the default bucket:

• functions.storage.object() to listen for object changes on the default storage
• functions.storage.bucket('bucketName').object() to listen for object changes on a particular bucket

For example, consider the code snippet of the functions:

exports.generateThumbnail = functions.storage.object().onChange((event)=>{
// ...
});

Most of the time, developers need not download or upload the files from storage. Sometimes, we might have to generate a thumbnail for the uploaded files. Cloud functions offer an efficient image processing program called ImageMagick that can perform most trivial image processing operations. Consider...