init = function (elementContainer) {
  elementContainer_ = elementContainer

  // Get correct em/ex values by creating a temporary SVG.
  const svg = document.createElementNS(NSSVG, 'svg')
  document.body.append(svg)
  const rect = document.createElementNS(NSSVG, 'rect')
  rect.setAttribute('width', '1em')
  rect.setAttribute('height', '1ex')
  rect.setAttribute('x', '1in')
  svg.append(rect)
  const bb = rect.getBBox()
  svg.remove()

  const inch = bb.x
  typeMap_ = {
    em: bb.width,
    ex: bb.height,
    in: inch,
    cm: inch / 2.54,
    mm: inch / 25.4,
    pt: inch / 72,
    pc: inch / 6,
    px: 1,
    '%': 0
  }
}
Initializes this module.

@function module:units.init
@param {module:units.ElementContainer} elementContainer - An object implementing the ElementContainer interface.
@returns {void}