title: addEventListener onload can be set or not
body: <p>I have the follow code</p>
  
  <pre><code>cost.addEventListener('keyup', updateInput);
  quantity.addEventListener('keyup', updateInput);
  </code></pre>
  
  <p>they update inputs if I change something but I have a input that must be autofilled when page load</p>
  
  <p>The input 1 has the product price cost comming from MySQL
  I have another input quantity with default value set to 1</p>
  
  <p>The input 3 changes to total cost perfect using cost * price IF I change quantity manually but when page load it show some addEventListener to the cost * quantity onload and not only when I manually do it editing quantity?</p>
  
  <p>something like</p>
  
  <pre><code>totalcost.addEventListener('onpageload', updateInput);
  </code></pre>