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

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

js

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

const startRangeOffset = range.startOffset;