title: Decrements time in javascript
body: <p>(second.innerHTML) -1 that worked but (num.innerHTML) -1 that not working why? </p>
  
  <pre><code>function doDcrements() {
       var hidden = document.getElementById('hidden');
       var second = document.getElementById('second');  // the second is 20.
       var loopTimer = 0;
       if (second.innerHTML != "0") {
           second.innerHTML = (second.innerHTML) -1;
           second.style.color = "blue";
           loopTimer = setTimeout('doDecrements()',1000);
       }else {
           second.style.color = "grey"; 
           hidden.style.display = "block";   
       }
   } 
  </code></pre>
  
  <p>.....................................................................................................................................................................</p>
  
  <pre><code>function doDcrements() {
           var hidden = document.getElementById('hidden');
           var second = document.getElementById('second'); // the second is 20. 
           var loopTimer = 0; 
           var num = document.getElementById('num'); // the number is 20. 
           if (second.innerHTML != "0") {
               second.innerHTML = (num.innerHTML) -1;
               second.style.color = "blue";
               loopTimer = setTimeout('doDecrements()',1000);
           }else {
               second.style.color = "grey";  
               hidden.style.display = "block";   
           }
       } 
  </code></pre>
  
  <p>when I create it by for loop it not happens :</p>
  
  <pre><code>function doDcrements() {
      var hidden = document.getElementById('hidden');
      var second = document.getElementById('second');
      for (i=20; i&lt;=0; i--) {
             if (second.innerHTML != "0") {
               second.innerHTML = i;
               second.style.color = "blue";
               loopTimer = setTimeout('doDecrements()',1000);
           }else {
               second.style.color = "grey";  
               hidden.style.display = "block";   
           }
      }
  }
  </code></pre>
  
  <p>html code: </p>
  
  <pre><code>&lt;div id="hidden"&gt;started&lt;/div&gt;
  &lt;p id="second"&gt;20&lt;/p&gt;
  &lt;div onClick="doDcrements();"&gt;Download&lt;/div&gt; 
  </code></pre>