JS两个数组合并后获取未重复的值

var projectsId=[1,2,3,4,5,6,add,7,8],newArr=[1,2,3,5,7,8,10], arr3=[];
for (var key = 0; key < projectsId.length; key++) {
          var stra = projectsId[key];
          var count = 0;
          for (var j = 0; j < newArr.length; j++) {
            var strb = newArr[j];
            if (stra == strb) {
              count++;
            }
          }
          if (count === 0) {
            arr3.push(stra);
          }
        };

console.log(arr3)