title: javascript addEventListener function parameters
body: <p>I am trying to capture the <code>screenX</code> and <code>screenY</code> value on each time mouse click on my canvas, so I use the <code>addEventListener</code>but the thing I got a little bit confused is: </p>
  
  <pre><code>canvas = document.getElementById('theCanvas');
  ctx = canvas.getContext('2d');
  
  window.addEventListener("click",function(event){
    console.log(event)
  });
  </code></pre>
  
  <p>after I find the clientX and clientY value which indicates my mouse x/y position on the screen in the console. I am a bit confused at when I tried to replace the event parameters with any other word or variables, it still did the same output in the console just like:</p>
  
  <pre><code>window.addEventListener("click",function(b){
    console.log(b)
  });
  </code></pre>
  
  <p>I am curious is that no matter what parametersI have passed into the function() here, will it always return the everything on the window object? I have read the article on the <a href="https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener" rel="nofollow noreferrer">https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener</a> but it didn't cover this. so may I get a help with my curiosity?</p>