title: const doesn't seem to pass value through functions
body: <p>I define two DOM selectors as constants but I can't seem to call them through functions. Essentially I should be able to pass two constants as arguments of a function where one gets it's display style set to block and the other set to none.</p>
  
  <p>My JS is:</p>
  
  <pre><code>const divOne = document.querySelector("#divOne");
  const divTwo = document.querySelector("#divTwo");
  
  function showHide(show, hide){
      show.style.display = "block";
      hide.style.display = "none";
  }
  
  function changeDisplay(arg) {
      //do some other bits
      showHide(divOne, divTwo);
  }
  </code></pre>
  
  <p>But this doesn't seem to change and I get an error</p>
  
  <pre><code>Uncaught TypeError: Cannot read property 'style' of null
          at showHide
  </code></pre>
  
  <p>Am I not able to pass querySelectors through functions?</p>