The read-only startContainer property of the AbstractRange interface returns the Node in which the start of the range is located.
To change the start position, use the Range.setStart() method or a similar one.
The Node inside which the start position of the range is found.
const range = document.createRange();
range.setStart(startNode, startOffset);
range.setEnd(endNode, endOffset);
const startRangeNode = range.startContainer;