disabling the back button with js

Does anyone konw how to disable the back button with javascript? I've been searching, but haven't found a way to truly disable it and someone is telling me that they've seen it before (I've never seen it).

I know the tricks like

onLoad="if(history.length>0)history.go(+1)"

or

location.replace(this)


but that's not what I'm looking for.