Uncaught referenceError: RGraph is not defined problem when upgrading to PHP 8.1

Question

When I use PHP 8.1, my RGraph chart does not work, the following error notice appeared:

uncaught referenceError: RGraph is not defined

I use the simple code as presented in the example on rgraph.net:

new RGraph.Bar{(
id: "cvs",
data: data,
.
.
.
)}.grow()

even if I use:

var bar = new RGraph.Bar{( ......)}

it still has the same error notice.

I hope this problem can be solved by define the RGraph, but it is not constant.