​

    var teams = [];

    var taskobj = [

          {'taskno':'a', 'team':'1,2'},

          {'taskno':'b', 'team':'3,4'},

          {'taskno':'c', 'team':'2,4'},

        ];

​

    taskobj.map(obj => {

      var teamSplit = obj.team.split(',');

      teams = [...teams, ...teamSplit];

    })

    var uniqTeams = _.uniq(teams);

    console.log('teams', teams);

    console.log('uniqTeams', uniqTeams)