vue element pickdate

<link rel="stylesheet" href="//unpkg.com/element-ui@2.9.1/lib/theme-chalk/index.css">
<script src="//unpkg.com/vue/dist/vue.js"></script>
<script src="//unpkg.com/element-ui@2.9.1/lib/index.js"></script>
        <div class="block"  id="app">
            <el-date-picker v-model="value"
                            type="daterange"
                            value-format="yyyy-MM-dd"
                            range-separator="至"
                            start-placeholder="开始日期"
                            end-placeholder="结束日期">
            </el-date-picker>
        </div>


<script>

   var dd= new Vue({
        el: ‘#app‘,
        data: {
            value: ‘‘,
        }
    })


    
</script>