How to use v-on:scroll to listen for scrolling events in Vue

Vue is one of the more popular front-end frameworks currently. In addition to common event monitoring, Vue also provides an instruction for monitoring scrolling events, namely v-on:scroll. This article will introduce in detail how to use v-on:scroll to listen for scroll events in Vue.

1. Basic usage of v-on:scroll directive

The v-on:scroll directive is used to monitor the scrolling events of DOM elements. Its basic usage is as follows:

<div v-on:scroll="scrollHandler"></div>

where , scrollHandler is a custom scroll event processing function.

2. Use v-on:scroll to monitor the scrolling event of the window object

If you want to monitor the scrolling event of the browser window, you need to bind the v-on:scroll instruction to the window object. , the code is as follows:

<template>
  <div>
    <p>当前滚动位置：{{ scrollTop }}</p>
    <div style="height: 2000px;" v-on:scroll="windowScroll"></div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      scrollTop: 0,
    };
  },
  methods: {
    windowScroll() {
      this.scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
    },
  },
};
</script>

In the above code, we use a variable scrollTop to save the current scroll position, and then bind the v-on:scroll instruction to a div element with a fixed height, so that It can be scrolled. In the scroll event handling function windowScroll, we obtain the current scroll position through document.documentElement.scrollTop || document.body.scrollTop and assign it to the scrollTop variable. In this way, every time the window is scrolled, the windowScroll method will be triggered and the current scroll position will be updated.

3. Use v-on:scroll to listen to the scrolling event of the component

If you want to listen to the scrolling event in the Vue component, you can bind the v-on:scroll directive to the root of the component. element and add the corresponding scroll processing function in the component.

<template>
  <div style="height: 200px; overflow-y: scroll;" v-on:scroll="scrollHandler">
    <ul>
      <li v-for="item in list">{{ item }}</li>
    </ul>
  </div>
</template>

<script>
export default {
  data() {
    return {
      list: ["item1", "item2", "item3", "item4", "item5"],
    };
  },
  methods: {
    scrollHandler(event) {
      console.log(event.target.scrollTop);
    },
  },
};
</script>

In the above code, we use a div element with a fixed height and scrollable area, and then bind the v-on:scroll directive to the element so that it can listen to scroll events. In the scroll event processing function scrollHandler, we can get the current scroll position through event.target.scrollTop.

4. Use the debounce function to optimize scrolling event processing

In actual development, we may need to perform some complex operations in the scrolling event processing function, such as updating page content and loading more data Etc., these operations are time-consuming, and if performed directly every time you scroll, it may cause delays on the page. In order to avoid this situation, we can use the debounce function to optimize the scroll event handling function.

The debounce function is a commonly used function throttling method. It allows a function to be executed only once within a certain period of time, thereby reducing the amount of calculations on the page. We can use it to optimize scroll events.

<template>
  <div style="height: 200px; overflow-y: scroll;" v-on:scroll="scrollHandlerWithDebounce">
    <ul>
      <li v-for="item in list">{{ item }}</li>
    </ul>
  </div>
</template>

<script>
import { debounce } from "lodash";

export default {
  data() {
    return {
      list: ["item1", "item2", "item3", "item4", "item5"],
    };
  },
  methods: {
    scrollHandler() {
      console.log(event.target.scrollTop);
    },
    scrollHandlerWithDebounce: debounce(function (event) {
      this.scrollHandler(event);
    }, 300),
  },
};
</script>

In the above code, we use the debounce function provided by the lodash library, wrap the scroll event handling function scrollHandler as scrollHandlerWithDebounce, call scrollHandler in this function, and set the anti-shake time to 300ms to make the scroll event The processing function is executed at most once within 300ms.

Summary

Using the v-on:scroll directive can easily monitor the scrolling events of DOM elements. At the same time, using the debounce function can effectively avoid excessive calls of the scrolling event processing function and optimize page performance. At the same time, we can also bind the v-on:scroll instruction to the root element of the window object or component to implement scrolling event monitoring in different scenarios.

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