For example, I merged the cells $B$2:$C$3 and set the outer border to red. I get each cell through EXCELJS, with only the information for the top and left borders.
Then I merged $B$5:$C$6 and set only the top and left borders. The resulting border information is the same as $B$2:$C$3.
So how do I know if the right and bottom borders have color settings?