The extension is triggered by default on saving (configurable in the extension settings) or by the Command Palette (a keybinding can be assigned there with the cog icon).
The extension will also format all open editors with pending changes when "Save All" is triggered from VS Code (look in Limitations for more details on this).
How to Use
The extension will be triggered when saving a file with one of the file extension mentioned in the description.
This can be toggled in the settings:
or in the settings.json:
The command can also be separately triggered from the Command Palette. The command ignores the setting to trigger the extension on save:
When activating "Save All" with VS Code only editors in a dirty state are saved, not the currently open editor (if not dirty). This means if an editor with unused imports is open with no pending changes then the extension will not be triggered
Saving an editor directly on the other hand always triggers the save event on the open editor so the extension will be triggered (if enabled)
The extension keeps tracked of the "visited" editors (since there's no way currently to get them from the api). This means that if some files are open with pending changed, VS Code is closed and re-opened and "Save All" is triggered then these files will not be formatted