title: Trigger mouse wheel scroll event - puppeteer
body: <p>I have a script in which I need to test the scrolling functionality on my page.  I have two scroll bars, one for the browser window and another for my grid in which I have implemented infinite scroll.  I am testing the browser window scroll like so:</p>
  
  <pre><code>(async () =&gt; {
  
      const innerWidth = await page.evaluate(_ =&gt; { return window.innerWidth} );
      const innerHeight = await page.evaluate(_ =&gt; { return window.innerHeight} );
      const mouse = page.mouse
      await mouse.move(innerWidth/2, innerHeight/2);
  
      await page.waitFor(500);
  
      // Scroll Window
      page.evaluate(_ =&gt; {
          window.scrollBy(0, innerHeight);
      });     
      ...
  }();
  </code></pre>
  
  <p>This works fine for the window scroll, however, I cannot use this to test the mouse wheel scroll in the grid.  I understand that there is a way to create a mouse wheel event in JQuery like so:</p>
  
  <pre><code>$(".testdiv").on('mousewheel', function(e){
    console.log(e);
  
  })
  var event = jQuery.Event( "mousewheel" );
  event.deltaY = -1;
  $(".testdiv").trigger(event); 
  </code></pre>
  
  <p>I need to do this in pure JS.  Is there a way to implement this in my script with pure JS?</p>