A simple function for positioning one DOM element relative to another DOM element (anchor element).
It is useful for implementing something like tooltips, dropdown/popups with support for these features:
- Automatically reposition element with best alternative placement if element renders out of browser view port.
 - Supports 12 placements options.
 
- up-left, up-center, up-right
 - down-left, down-center, down-right
 - left-top, left-middle, left-bottom
 - right-top, right-middle, right-bottom
 
- Customizable distance and offset
 
import positionElement from 'position-element';
const config = {
  element: document.getElementById('subject'),
  anchorElement: document.getElementById('anchor'),
  preferredPlacement: 'down-center',
  distance: 10,
  alignmentOffset: 0,
  autoReposition: true,
};
positionElement(config);
positionElementwill do the measurement and set element'sposition: absolute,leftandtopstyle for you.- However, it is important for you to set the right 
positionstyle (e.g.position:relative) for the common container of both the anchor element and the positioning element.