var students=[

{name: "vehicleTravelLicenseCopyBack", id: "a1"},

{name: "vehicleTravelLicenseCopyFront", id: "a2"},

{name: "idCardBack", id: "a3"},

{name: "idCardFront", id: "a4"}

      ]

        

        var arr=[];

        for(var i=0;i<students.length;i++){

             

           arr.push(students[i]['id']);

        }

         

        console.log(arr,'4555');