The last example of tutorial "Using OpenCV.js In Node.js" failed

When i try to execute the last example of tutorial “Using OpenCV.js In Node.js”,i got an error:
TypeError: Cannot read property ‘mount’ of undefined,the opencv.js build myself is 4.5.4 and work well in other examples of the tutorial.
I download some official versions of opencv.js and try it ,then i found that the only the versions after 3.4.8/4.1.2 execute well.I read the update log,but didn’t find the correlative explain. How to fix the problem, i want to know why the problem occurred .Because i want to build opencv.js myself.Any help will be appreciated.