Is element in view? A cross-browser way to check if a specific element is in viewport

is_el_in_view.js

// check if el is in view
function is_el_in_view(el, full_el_visible) {
  if (!el) return false;
  
  // should we return true if the element is only partially visible (default)
  full_el_visible = typeof full_el_visible != "undefined" ? full_el_visible : false;
  
  var el_pos = get_absolute_offset(el),
    el_h = el.offsetHeight,
    window_h = window.innerHeight || document.documentElement.clientHeight,
    viewport_y = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop,
    viewport_bottom_y = viewport_y + window_h,
    el_pos_bottom = el_pos + el_h;

  if ( (viewport_bottom_y >= el_pos && viewport_y <= el_pos) // is the element top between the viewport range (top and bottom)
    || (viewport_bottom_y >= el_pos_bottom && viewport_y <= el_pos_bottom) // is the element bottom between the viewport range (top and bottom)
    || (viewport_y >= el_pos && viewport_bottom_y <= el_pos_bottom)) { // is the element bigger than the viewport?
    // ok, we can see the element, at least part of it. we should check if the whole element is visible
    if (full_el_visible) {
      if ( (el_pos <= viewport_bottom_y && el_pos_bottom > viewport_bottom_y) // partially visible in bottom
        || (el_pos <= viewport_y && el_pos_bottom > viewport_y)) { // partially visible in top
        // only partially visible, return false
        return false;
      } else {
        // full visible element!
        return true;
      }
      
    } else {
      return true;
    }
    
  } else {
    return false;
  }
  function get_absolute_offset(el) {
    var offset = 0;
    while (el != null) {
      offset += el.offsetTop;
      el = el.offsetParent;
    }
    return offset;
  }
}