How to assign the same keyboard shortcut to two elements?

Question

JavaScript

There is this code:

e2_ctrl_navi = function(event) {
  if (window.event) event = window.event
  var target = (event.srcElement || event.target).tagName;
  if (/textarea|input/i.test(target)) return

  if (
    (document.e2.mac && event.altKey) || (!document.e2.mac && event.ctrlKey)
  ) {
    var link = null
    if (37 == event.keyCode) link = document.getElementById('link-prev')
    if (39 == event.keyCode) link = document.getElementById('link-next')
    if (38 == event.keyCode) link = document.getElementById('link-later')
    if (40 == event.keyCode) link = document.getElementById('link-earlier')
    if (link && link.href) {
      location.href = link.href
      if (window.event) window.event.returnValue = false
      if (event.preventDefault) event.preventDefault()
    }
  }
}

All four idhave different keyboard shortcuts assigned.
And I need something like this:

if (37 == event.keyCode) link = document.getElementById('link-prev')
if (39 == event.keyCode) link = document.getElementById('link-next')
if (39 == event.keyCode) link = document.getElementById('link-later')
if (37 == event.keyCode) link = document.getElementById('link-earlier')

For #link-prevand #link-earliermust be the same key combination. Likewise for #link-nextand #link-later.
But it doesn't work like this.

PS At the same time, only one of the pairs occurs on the page, so there should be no conflicts.