Vue 获取 Width 和 Height

获取Div的 Width 和 Height

<div>
    <div id="bg-prev" ref="el_div">
    </div>
<div>

mounted() {
  	this.getWindowWidth()
},
methods: {
    getWindowWidth() {
        this.x = this.$refs.el_div.clientWidth;
    }
}