Get id of parent element of currently clicked element in AngularJS

It should be parentNode, not just parent:

alert(obj.target.parentNode.id);

Also attributes is redundant as you can access id property directly.

But note, that since you have ngRepeat, it will create invalid markup, since ids are going to be duplicated. You probably want to fix this too, maybe like this or use classes:

<div id="d8{{$index}}" class="menutitles ng-scope" ng-repeat="title in list">
    <div class="right" ng-click="showsubmenu()">+</div>
   <div class="left" ng-click="showsubmenu()">Unit 9</div>
</div>

<div id="d8" class="menutitles ng-scope" ng-repeat="title in list">
    <div class="right" ng-click="showsubmenu()">+</div>
   <div class="left" ng-click="showsubmenu()">Unit 9</div>
</div>

It should be enough :D

function showsubmenu($event){
    $($event.target).parent();

}

Have a nice day