因為搞了好幾天也沒在網上找到答案。所以用了自己想的辦法，後來感覺還是很笨的辦法，不過總算解決了

screen(value4,value5,value6,currentPage) {
      this.axios
      .get(`/teacher/mapping/list`, {
        schoolId: this.value4 ,
        gradeId: this.value5 ,
        subjectId: this.value6 ,
        pageNum: this.currentPage,
        size: 10
      })
      .then(res => res.data)
      .then(data => {
        if(data.code == 200) {
          var arr = []//陣列1
          var arr1 = []//陣列2
          var arr2 = []//陣列3
          //如果三個中任何一個被選擇的話執行這個
          for(let i=0;i<this.list.length;i++){
            if(this.value5 == this.list[i].gradeId){
              arr.push(this.list[i])
            }
            if(this.value4 == this.list[i].schoolId){
              arr.push(this.list[i])
            }
            if(this.value6 == this.list[i].subjectId){
              arr.push(this.list[i])
            }
          }
          // 如果三個中有任意兩個被選擇的話執行arr1
          for(var j=0;j<this.list.length;j++){
            if(this.value5 == this.list[j].gradeId && this.value4 == this.list[j].schoolId){
              arr1.push(this.list[j])
            }
            if(this.value4 == this.list[j].schoolId  && this.value6 == this.list[j].subjectId){
              arr1.push(this.list[j])
            }
            if(this.value6 == this.list[j].subjectId && this.value5 == this.list[j].gradeId){
              arr1.push(this.list[j])
            }
          }
          // 如果三個都被選擇的話執行arr2
          for(var k=0;k<this.list.length;k++){
            if(this.value5 == this.list[k].gradeId && this.value4 == this.list[k].schoolId && this.value6 == this.list[k].subjectId){
              arr2.push(this.list[k])
            }
          }

          //下面個判斷出來的結果必須放在最後。不然會出錯
          if(this.value4 != '' || this.value5 != '' || this.value6 != ''){
            this.list = arr
          }
          if(this.value5 != '' && this.value4 != '' || this.value4 != '' && this.value6 != '' || this.value6 != '' && this.value5 != ''){
            this.list = arr1
          }
          if(this.value6 != '' && this.value5 != '' && this.value4 != ''){
            this.list = arr2
          }
        }
      })
    },
 

當點選篩選按鈕的時候改變下面的table表格的資料

以後如果有更好的辦法會更新