Randomising Value in Dat.GUI

I'm using dat.gui to control values but want to add a button to randomise the value. Is there a way to do this? I have the randomise button but I cannot figure out how to reference the parameter to change its value.

Basic code is something like:

const params = {}
params.num = 20

gui.add(params, 'num').onChange(doSomething)

//on clicking the 'Randomise' button I would essentially like this to happen:

gui.(params, 'num').setValue( randomValue ).onChange(doSomething)

Is there some way I can reference the parameter, and then set its value to x? Thanks in advance!