Using nexttick in vue3 does not take effect

With the release of Vue3, many developers began to try to use the new version of the framework to build complex web applications. However, some developers have found that there are some problems when using Vue3's nextTick method. This article discusses this problem and how to resolve it.

What is nextTick method?

In Vue2, the nextTick method is a common method to solve asynchronous DOM updates. It can execute the callback function before the next DOM update cycle. Doing this avoids inconsistencies when updating the DOM. For example, when modifying the props of the parent component, the props of the child component may still be the old value. In this case, the nextTick method can be used to ensure that the child component uses the latest props value.

In Vue3, the nextTick method still exists. But unlike Vue2, Vue3 uses a new reactive system that integrates better with modern JavaScript syntax and build tools. This also means some changes in the way the nextTick method is used in Vue3.

Usage of nextTick method in Vue3

In Vue3, the use of nextTick method is similar to Vue2. You can access it using Vue3's global API:

import { nextTick } from 'vue';

// 假设 data.count 初始值为 0
console.log('before update: ', data.count);

nextTick(() => {
  console.log('after update: ', data.count);
});

data.count++; // 修改data.count的值

// 输出:
// before update: 0
// after update: 1

In the above example, we use the nextTick method to ensure that the console.log method is run after the DOM has been updated. However, sometimes the nextTick method does not take effect, that is, the callback function is not executed. Next, we'll discuss what might be causing this problem.

Possible reasons why the nextTick method does not take effect

1. Using nextTick in the component life cycle hook function

When using the nextTick method, please ensure that you are in the DOM This method is called before the update cycle. If you call the nextTick method in a life cycle hook function, the callback function may not be executed. For example, using the nextTick method in Vue3's mounted hook function will not take effect.

In Vue3, if you need to run some code after the component is mounted, consider using the onMounted hook function instead. For example:

import { onMounted, nextTick } from 'vue';

export default {
  setup() {
    onMounted(() => {
      nextTick(() => {
        console.log('after update');
      });
    });
  }
}

2. Use setTimeout instead of nextTick

In Vue2, maybe you will use the setTimeout method instead of the nextTick method. However, using setTimeout in Vue3 may cause the responsive system to be unable to update the DOM in time. So if possible use nextTick method.

For example, when using the setTimeout method, you may encounter the problem of being unable to update the DOM:

import { ref, nextTick } from 'vue';

export default {
  setup() {
    const count = ref(0);

    function handleClick() {
      setTimeout(() => {
        count.value++;
      }, 0);
    }

    return {
      count,
      handleClick
    }
  }
}

In the above example, we use the setTimeout method to update the value of data.count. However, in this case, the component cannot detect that the value of count has changed and therefore cannot update the DOM correctly. The correct way is to use the nextTick method:

import { ref, nextTick } from 'vue';

export default {
  setup() {
    const count = ref(0);

    function handleClick() {
      nextTick(() => {
        count.value++;
      });
    }

    return {
      count,
      handleClick
    }
  }
}

In the above example, we use the nextTick method instead of the setTimeout method to update the value of data.count.

Conclusion

When using the nextTick method of Vue3, sometimes you may encounter the problem that the callback function is not executed. This article describes several possible causes and provides corresponding solutions. Keep in mind that in Vue3, the nextTick method is still the common way to handle asynchronous DOM updates.

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