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

**URL:** <https://forum.opencv.org/t/the-last-example-of-tutorial-using-opencv-js-in-node-js-failed/5643>\
**Category:** Uncategorized\
**Tags:** opencvjs, build\
**Created:** [October 15, 2021, 3:49am UTC](https://forum.opencv.org/t/the-last-example-of-tutorial-using-opencv-js-in-node-js-failed/5643 "2021-10-15T03:49:45Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![zxx0717](https://avatars.discourse-cdn.com/v4/letter/z/df788c/32.png) [@zxx0717](https://forum.opencv.org/u/zxx0717)\
**Post date:** [October 15, 2021, 3:49am UTC](https://forum.opencv.org/t/the-last-example-of-tutorial-using-opencv-js-in-node-js-failed/5643/1 "2021-10-15T03:49:45Z")

</div>

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.