|Helper function for getting mouse position in major browsers

index.js

const getMousePosition = (e) => {
  let posX = 0, posY = 0;
  if (!e) e = window.event;
  if (e.pageX ¦¦ e.pageY) {
    posX = e.pageX;
    posY = e.pageY;
  } 
  // This only applies in IE
  else if (e.clientX ¦¦ e.clientY) {
    const eventDoc = (e.target && e.target.ownerDocument) ¦¦ document;
    const doc = eventDoc.documentElement;
    const body = eventDoc.body;
    posX = e.clientX + (doc && doc.scrollLeft ¦¦ body && body.scrollLeft ¦¦ 0) - (doc && doc.clientLeft ¦¦ body && body.clientLeft ¦¦ 0)
    posY = e.clientY + (doc && doc.scrollTop ¦¦ body && body.scrollTop ¦¦ 0) - (doc && doc.clientTop ¦¦ body && body.clientTop ¦¦ 0)
  }
  return { x: posX, y: posY };
}