从下拉菜单Angular中删除选定的值

Question

有4个相互关联的选择选项，因此当我从第一个选择一个选项时，应该从其他三个选择选项中删除该值

// LIST TARGET SLAB
  getTargetSlab() {
    this.riderservice.getTargetSlab().subscribe(res => {
      this.target_slab = res['success'].data;
      this.target_slab1 = res["success"].data;
      this.target_slab2 = res["success"].data;
      this.target_slab3 = res["success"].data;
      this.target_slab4 = res["success"].data;
    });
  }

// FUNCTION TO REMOVE SELECTED TARGET PLAN

  removeSelectedTargetSlab(index, slab) {
    switch (index) {
      case 1: {
        this.target_slab2 = this.target_slab.filter(element => element != slab);
        this.target_slab3 = this.target_slab.filter(element => element != slab);
        this.target_slab4 = this.target_slab.filter(element => element != slab);
        break;
      }
      case 2: {
        this.target_slab1 = this.target_slab1.filter(element => element != slab);
        this.target_slab3 = this.target_slab3.filter(element => element != slab);
        this.target_slab4 = this.target_slab4.filter(element => element != slab);
        break;
      }
      case 3: {

        this.target_slab1 = this.target_slab1.filter(element => element != slab);
        this.target_slab2 = this.target_slab2.filter(element => element != slab);
        this.target_slab4 = this.target_slab4.filter(element => element != slab);
        break;
      }
      case 4: {
        this.target_slab1 = this.target_slab1.filter(element => element != slab);
        this.target_slab2 = this.target_slab2.filter(element => element != slab);
        this.target_slab3 = this.target_slab3.filter(element => element != slab);
        break;
      }
    }

  }

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上面的代码是我尝试过的component.ts文件。

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