如何使FabricJS画布上的所有对象都作为一个组激活？

I'm trying to make it so whenever a button is clicked, all objects on the canvas are selected and put into a group so they're all manipulated together. I found a good example of the grouping and ungrouping of objects that almost works the way I need, however it requires the user to select the objects they want when I want all objects on the canvas to be grouped/ungrouped.I'm trying to make it so whenever a button is c