Selection: rangeCount property

The Selection.rangeCount read-only property returns the number of ranges in the selection.

Before the user has clicked a freshly loaded page, the rangeCount is 0. After the user clicks on the page, rangeCount is 1, even if no selection is visible.

A user can normally only select one range at a time, so the rangeCount will usually be 1. Scripting can be used to make the selection contain more than one range.

Gecko browsers allow multiple selections across table cells. Firefox allows to select multiple ranges in the document by using Ctrl+click (unless the click occurs within an element that has the display: table-cell CSS property assigned).

<table>
  <tr>
    <td>a.1</td>
    <td>a.2</td>
  </tr>
  <tr>
    <td>b.1</td>
    <td>b.2</td>
  </tr>
  <tr>
    <td>c.1</td>
    <td>c.2</td>
  </tr>
</table>

setInterval(() => {
  console.log(window.getSelection().rangeCount);
}, 1000);