get-selection-range-from-elm/dist/index.js

window.getSelection().rangeAt(0) but only if it exists & is within an element

"use strict";

module.exports = function (elm) {
  var selection = window.getSelection();

  if (selection.rangeCount === 0) {
    return null;
  }

  var range = selection.getRangeAt(0);
  var start = range.startContainer;
  var end = range.endContainer;

  return elm.contains(start) && elm.contains(end) ? range : null;
};