【项目需求】：两个下拉框之间选项关联

<el-select v-model="value1" placeholder="请选择">
    <el-option v-for="item in options" :key="item.value" :label="item.label"         
        :value="item.value":disabled="item.value == value2">
    </el-option>
</el-select>
<el-select v-model="value2" placeholder="请选择">
    <el-option v-for="item in options" :key="item.value" :label="item.label"     
        :value="item.value":disabled="item.value == value1">
    </el-option>
</el-select>

data () {
        return {
            options: [{
                value: '选项1',
                label: '黄金糕'
            }, {
                value: '选项2',
                label: '双皮奶',
            }, {
                value: '选项3',
                label: '蚵仔煎'
            }, {
                value: '选项4',
                label: '龙须面'
            }, {
                value: '选项5',
                label: '北京烤鸭'
            }],
            value1: '',
            value2: '',
        };
    },

<el-select v-model="value1" placeholder="请选择" @change="value1Change">
   <el-option v-for="item in value2Options" :key="item.value" :label="item.label" 
      :value="item.value">
   </el-option>
</el-select>
<el-select v-model="value2" placeholder="请选择" @change="value2Change">
   <el-option v-for="item in value1Options" :key="item.value" :label="item.label"         
      :value="item.value">
   </el-option>
</el-select>

data () {
        return {
            options: [{
                value: '选项1',
                label: '黄金糕'
            }, {
                value: '选项2',
                label: '双皮奶',
            }, {
                value: '选项3',
                label: '蚵仔煎'
            }, {
                value: '选项4',
                label: '龙须面'
            }, {
                value: '选项5',
                label: '北京烤鸭'
            }],
            value1: '',
            value2: '',
            value1Options: [],
            value2Options: [],
        };
    },
    mounted () {
        this.value1Options = this.value2Options = this.options;
    },
    methods: {
        value1Change (val) {
            console.log(val);
            this.value1Options = this.options.filter(item => {
                return item.value != val;
            })
            console.log(this.value1Options);
        },
        value2Change (val) {
            this.value2Options = this.options.filter(item => {
                return item.value != val;
            })
        },
    },