javascript to get paragraph of selected text in web page

This is actually rather hard to do because you have to consider six cases:

1. The selection is not within a paragraph (easy);
2. The entire selection is within one paragraph (easy);
3. The entire selection crosses one or more sibling paragraphs (harder);
4. The selection starts or ends in an element not within a paragraph (harder);
5. The paragraphs spanned are at different levels eg one is within a list item while two others are siblings of the list (even harder); and
6. Some combination of the above.

So firstly you have to decide how complete you want the solution to be. I’ll only cover the simplest cases of (1) and (2).

function getSelectedParagraphText() {
  if (window.getSelection) {
      selection = window.getSelection();
  } else if (document.selection) {
      selection = document.selection.createRange();
  }
  var parent = selection.anchorNode;
  while (parent != null && parent.localName != "P") {
    parent = parent.parentNode;
  }
  if (parent == null) {
    return "";
  } else {
    return parent.innerText || parent.textContent;
  }
}

Note: If you’re after tags too replace textContent with innerHTML.

Edit: Better version put in, including better browser compatibility.