Solve false for js once for all

function exists(e) {
  return {
    [false]: false,
    [void 0]: true
  }[{
    [void 0]: false,
    [{}]: false,
    [false]: false,
    [undefined]: false,
    [1 / 0]: false
  }[e]]
}


var a = ''
if (exists[a]) {
  //is really not null
} else {
  //is null
}