An integer value indicating the number of characters into the Node indicated by endContainer at which the final character of the range is located.

If the endContainer is a Node of type Text, Comment, or CDATASection, then the offset is the number of characters from the start of the endContainer to the boundary point of the range. For other Node types, the endOffset is the number of child nodes between the start of the endContainer and the boundary point of the range.

js

const range = document.createRange();
range.setStart(startNode, startOffset);
range.setEnd(endNode, endOffset);

const endRangeOffset = range.endOffset;