How do I get if statements in function with JavaScript?

So, I have been using if statements in JavaScript, but all it does is make my browser ignore that there is functions ANYWHERE.

Here's my code:

  define('SCRIPT_DEBUG', true);
  function start(){
   document.getElementById('c1').hidden="true";
   document.getElementById('gameplay').removeAttribute('hidden');
  }
  function enter(){
   var a = document.getElementById('f1');
   var b = document.getElementById('f2');
   var c = document.getElementById('f3');
   var d = a.innerHTML ** b.innerHTML;
   var e = document.getElementById('score');
   var f = document.getElementById('scorecopy');
   var g = document.getElementById('fcsncp');
   var h = document.getElementById('fcsn');
   var i = document.getElementById('f1ct');
   var j = document.getElementById('f2ct');
   var m = document.getElementById('f1cp');
   var n = document.getElementById('f2cp');
   if ( d = c.innerHTML ){
    f.innerHTML + 1 = e.innerHTML;
    e.innerHTML = f.innerHTML;
   }
  }

And if you looked, I added a debug I found on the, but it still didn't make it ignore the errors.