Select previous and next words when double clicking blank space in HTML with Javascript

I was trying to change the behaviour of an HTML page with Javascript so whenever I click a blank space in a text (not textArea) between two words, instead of selecting that blank space, it selects the words before and after the blank space. I was trying to do it this way, but I am not able to do it:

function getBothWords() {
  if (window.getSelection()) {
    var sel = window.getSelection();
    var blank = " ";
    if(sel == blank) {
      ...
    }
  }
}

I also was trying to play with:

window.getSelection().getRangeAt(0)

But still nothing. Any ideas? Thanks :)