Get element height with Vuejs

I want to get the height of a div in order to make the height of another div matching it. I used the method clientHeight, but It doesn’t return me the good value (smaller value). Actually, It seems to return a height before all elements are charged. After some research online, I tried to put a window.load() to delay until everything is charged but it doesn’t work as well. Some ideas ?

mounted () {
  this.matchHeight()
},
matchHeight () {
  let height = document.getElementById('info-box').clientHeight
}

<div class="columns">
  <div class="left-column" id="context">
  <p>Some text</p>
  </div>
  <div class="right-column" id="info-box">
    <img />
    <ul>
      some list
    </ul>
  </div>
</div>

Answer

The way you are doing it is fine. But there is another vue specific way via a ref attribute.

 mounted () {
   this.matchHeight()
 },
 matchHeight () {
   let height = this.$refs.infoBox.clientHeight;
 }

    <div class="columns">
        <div class="left-column" id="context">
            <p>Some text</p>
        </div>
        <div class="right-column" id="info-box" ref="infoBox"></>
            <img />
            <ul>
                some list
            </ul>
        </div>
    </div>

In this case, since you are just getting the value it really doesn’t matter whether you use your original getElementById approach or the vue specific ref approach. However if you were setting the value on the element then it’s much better to use the ref approach so that vue understands that the value has changed and won’t possibly overwrite the value with the original value if it needs to update that node in the DOM.

You can learn more here: https://v2.vuejs.org/v2/api/#vm-refs

Update

A few people had left comments that the above solution didn’t work for them. That solution provided the concepts but not full working code as example, so I have augmented my answer with the code below which demonstrates the concepts.

var app = new Vue({
    el: '#app',
    data: function () {
        return {
            leftColStyles: { },
            lines: ['one', 'two','three']
        }
    },
    methods: {
        matchHeight() {
            var heightString = this.$refs.infoBox.clientHeight + 'px';
            Vue.set(this.leftColStyles, 'height', heightString); 
        }
    },
    mounted() {
        this.matchHeight();
    }

});

.columns{width:300px}
.left-column {float:left; width:200px; border:solid 1px black}
.right-column {float:right; border:solid 1px blue; }

<div id="app">
    <div class="columns">
        <div class="left-column" id="context" v-bind:style="leftColStyles">
            <p>Some text</p>
        </div>
        <div class="right-column" id="info-box" ref="infoBox"> 
            <img />
            <ul>
                <li v-for="line in lines" v-text="line"></li>
            </ul>
        </div>
    </div>

</div>

 <script src="https://unpkg.com/vue@2.6.12/dist/vue.min.js"></script>
 

Here is a screenshot of the results in the browser:

Note:
My answer assumes that you are loading vue.js from a cdn or locally into the browser and executing it there. If instead you are running your code via the cli and my answer is not working for you, please see @mayank1513‘s answer instead.