vue calculates the height of the hidden page

As front-end pages become more and more complex, we often need to use various techniques to achieve some seemingly simple requirements. For example, we need to calculate the height of hidden elements on the page for subsequent processing. What should we do at this time? The answer is to use Vue to calculate the height of the hidden page.

Vue is a front-end framework that builds a responsive component system for building web interfaces. It organizes the user interface through an abstract, data-based view component model and declaratively binds the DOM to the underlying Vue instance through a simple template syntax. Vue also provides some auxiliary functions, such as calculated properties, observers, components, etc., which can very conveniently solve many problems in front-end development, including calculating the height of the hidden page.

So, we can calculate the hidden page height through calculated properties. Here is a simple example:

<template>
  <div>
    <div class="content" ref="content">
      <p v-for="index in 10">这是第{{index}}段文字</p>
    </div>
    <div class="show-more" @click="showMore">{{showMoreText}}</div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      isShowMore: false,
      showMoreText: '显示更多'
    }
  },
  computed: {
    contentHeight() {
      // 获取内容区高度
      return this.$refs.content.scrollHeight + 'px'
    }
  },
  methods: {
    showMore() {
      this.isShowMore = !this.isShowMore
      if (this.isShowMore) {
        this.showMoreText = '收起'
      } else {
        this.showMoreText = '显示更多'
      }
    }
  }
}
</script>

<style>
.content {
  overflow: hidden;
  max-height: 200px;
  transition: max-height .3s ease;
}

.show-more {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 50px;
  color: #fff;
  background: #f60;
  cursor: pointer;
}
</style>

The above code implements a component with a "Show More" button. By default, the content area displays content up to 200 pixels high. When the "Show More" button is clicked, the content area expands to display all content. We need to calculate the height of the content for subsequent processing.

In Vue, we can use the computed attribute to calculate the height of page elements. In this example, we use this.$refs.content.scrollHeight to get the height of the content area. $refs is a special property provided by Vue, used to obtain DOM elements or sub-component instances inside the component. In the code, we use ref="content" to identify the DOM element in the content area, and then use this.$refs.content.scrollHeight in the computed attribute to get the height of the element. It should be noted that this calculated property is only calculated when the content area is expanded.

This calculated attribute can realize many similar scenarios, such as calculating the width of an element, calculating the position of an element, etc. In general, Vue's calculated properties are a very practical tool that can greatly improve our development efficiency.

In addition to calculated properties, Vue also provides many other functions, such as watchers, components, etc., which can help us develop complex front-end applications more conveniently. In future development, we should use these tools as much as possible to better complete our tasks.

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