element tree单选

                   <el-tree
                        :data="depData"
                        show-checkbox
                        node-key="id"
                        ref="treedep"
                        default-expand-all
                        @check-change = "change2"
                        :check-strictly="true" 
                        :props="defaultProps">
                   </el-tree>

            selectOrg: {

             orgsid: []

            }   

 

        change2(data,checked,msg3){

                 const indexs = this.selectOrg.orgsid.indexOf(data.id)

                if (indexs < 0 && this.selectOrg.orgsid.length === 1 && checked) {

                console.log('only one')

                this.$message({

                    message: '只能选择一个部门！',

                    type: 'error',

                    showClose: true

                })

                this.$refs.treedep.setChecked(data, false)

                } else if (this.selectOrg.orgsid.length === 0 && checked) {

                this.selectOrg.orgsid = []

                this.selectOrg.orgsid.push(data.id)

                } else if (

                indexs >= 0 &&

                this.selectOrg.orgsid.length === 1 &&

                !checked

                ) {

                this.selectOrg.orgsid = []

                }

      },