Writing an NWB File ​

Using the file you provided in the last tutorial—or using the streamed DANDI file for dummy data—we'll experiment with updating metadata. On any part of the NWBFile, you can simply update the property to change its representation in memory.

file.file_create_date = Date.now()

The WebNWB API automatically conforms values provided by users to the NWB Schema.

For instance, the file_create_date value should be an array of isodatetime values. So our Date.now() output will be converted into an ISO string inside an array!

Additionally, WebNWB ensures that values carry all of their metadata with them. Instead of a standard string, then, the new file_create_date string will be created using the String constructor and the Array will have additional properties such as doc, dims, dtype, name, and shape from the NWBFile schema entry.

console.log(file.file_create_date) // Will look like: [ String('2023-02-08T22:09:34.901Z') ]

Saving Changes ​

While all of your changes have been registered in memory, we still have to save them to local storage using the save command.

const filename = await io.save(file) console.log('Saved:', filename)

Once saved, you can access this file by name using the load function.

const fileFromLocalStorage = await io.load(filename) console.log('File from local storage:', fileFromLocalStorage)

Downloading a NWB File from the Browser ​

Finally, if you'd like to download the updated file to your local computer, simply use the download function.

io.download(filename)