JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/ui-lightness/jquery-ui.css">
<div id="element">
  Blah blah blah.
  <div>Header</div>
  ...
</div>

JavaScript

var first_line = $("#element")
                .contents()
                 .filter(function() { 
                     return !!$.trim(this.innerHTML||this.data);
                 })
                  .first();

alert(first_line.text());