Object array merges elements according to a field

Such as ：

// arr Is the initial array ,key For what needs to be dealt with key name 
	unique (arr, key) {
      var tempArr = []
      var newArr = []
      for (let i = 0; i < arr.length; i++) {
        if (tempArr.indexOf(arr[i][key]) === -1) {
          newArr.push({
            name: arr[i].name,
            activity: arr[i].activity
          })
          tempArr.push(arr[i][key]);
        } else {
          for (let j = 0; j < newArr.length; j++) {
            if (newArr[j][key] == arr[i][key]) {
              newArr[j].activity = newArr[j].activity.concat(arr[i].activity)
            }
          }
        }
      }
      return newArr
    }

Output ：