selection

select text

HTML

<div>
  <p>Hello World!</p>
  <p>The fucking world!</p>
</div>

<button>get selected</button>

JavaScript

document.querySelector('button').addEventListener('click', function(){
    var sel = window.getSelection();
    if(sel){
        alert('You selected + ' + sel);
    }else{
        alert('you haven\'t selected anything');
    }
}, false);