code: function (obj) {
        if (!obj) return
        diffTitle.before = opt.complement
        var title = obj.inner + ' ' + (obj.separator || opt.separator) +
          ' ' +  (obj.complement || opt.complement)
        window.document.title = title.trim()
      }
docs: Change window.document title
  @type {Function}
  @param  {Object} obj