$ npm install bloody-offset
var offset = require("bloody-offset")
returns element's offset
object.height
: integer, element's heightobject.width
: integer, element's widthobject.top
: integer, element's top offsetobject.left
: integer, element's left offset
var elementOffset = offset(element)
lightbox.style.top = elementOffset.top + "px"
lightbox.style.left = elementOffset.left + "px"
lightbox.style.display = "block"