I am using opencv.js to get average color from a masked region, the API I am using is cv.meanStdDev. The code:

            let mask = cv.Mat.zeros(image.cols, image.rows, cv.CV_8UC3);
            let mean = new cv.Mat;
            let std = new cv.Mat;

            cv.meanStdDev(image, mean, std);

is good, but when I add the last 'mask' parameter:

            cv.meanStdDev(image, mean, std, mask);

in browser console it prints:

Uncaught 6577936

And the script stopped. Seems like the implementation of meanStdDev is broken?