当右侧下拉框选中为 长期有效,那么左侧输入框为禁用状态;

<el-form-item label="证明有效期" class="is-required">
                            <div v-for="(item,index) in form.arrayDat" :key="index" style="width: 100%;display: flex;justify-content: space-between;">
                                <div style="width: 85%;display: flex;justify-content: space-between;margin-bottom: 20px">
                                    <el-form-item style="width: 40%" :prop="'arrayDat.'+index+'.count'" :rules="[{required: true,message:'请输入',trigger: 'blur'}]">
                                        <el-input v-model="item.count" placeholder="请输入" :disabled="item.flag"/>
                                    </el-form-item>
                                    <el-form-item style="width: 50%" :prop="'arrayDat.'+index+'.deadline'" :rules="[{required: true,message:'请选择',trigger: 'change'}]">
                                        <el-select v-model="item.deadline" placeholder="请选择" @change="validChange">
                                            <el-option v-for="dict in prove_deadline" :key="dict.value" :label="dict.label"
                                                       :value="dict.value"></el-option>
                                        </el-select>
                                    </el-form-item>
                                </div>
                                <div style="width: 8%;display: flex;">
                                    <el-button icon="Plus" type="text" @click="add"></el-button>
                                    <div class="del" v-if="form.arrayDat.length > 1">
                                        <el-button icon="Minus" type="text" @click="del(index)"></el-button>
                                    </div>
                                </div>
                            </div>
                        </el-form-item>

const data = reactive({
    form: {
        // 新增行
        arrayDat: [{count:'',deadline:'',flag: false}]
    },
})
const { form } = toRefs(data);

 核心:

const validChange = (val) => {
    for (let i = 0; i < form.value.arrayDat.length; i++) {
        // 如果当前元素的 deadline 值为 3
        if (form.value.arrayDat[i].deadline == '3') {
            // 将对应的 flag 输入框设置为禁用状态
            form.value.arrayDat[i].flag = true;
        } else {
            // 否则设置为启用状态
            form.value.arrayDat[i].flag = false;
        }
    }
    console.log(form.value.arrayDat,'@@@')
}