Vue3中watch和watchEffect区别和用法

本文探讨了 Vue 3 中 watch 和 watchEffect 之间的差异，重点介绍了它们的用法和功能。 watch 是一个立即模式反应函数，在组件安装和数据更改时调用，而 watchEffect 是一个惰性模式 r

Vue3 中 watch 和 watchEffect 之间有什么明显区别？

Vue3 引入了一个新的反应性 API包括两个新函数：watch 和 watchEffect。这两个函数都允许您跟踪 Vue 组件中反应状态的更改，但它们以不同的方式实现。 watch 和 watchEffect 函数之间的主要区别是：watch and watchEffect. Both of these functions allow you to track changes to reactive state in your Vue components, but they do so in different ways. The main distinctions between the watch and watchEffect functions are:

• watch uses immediate mode reactive function, which means that the watcher function is called immediately after the component is mounted and whenever the observed data changes.
• watchEffect uses lazy mode reactive function which means that the effect function is only called when the observed data changes.

How do watch and watchEffect differ in their usage and functionality in Vue3?

watch

The watch function accepts two arguments:

1. A string or an array of strings representing the reactive properties that you want to watch.
2. A function that will be executed when the value of the observed properties changes.

<code>// Watch a single property
watch('count', () => {
  console.log(`The count has changed to ${count}`);
});

// Watch multiple properties
watch(['count', 'message'], () => {
  console.log(`The count or message has changed.`);
});</code>

watchEffect

The watchEffect function accepts only one argument:

1. A function that will be executed when the observed data changes.

<code>watchEffect(() => {
  console.log(`The count is now ${count}`);
});</code>

When and why would you choose to use watch or watchEffect in a Vue3 application?

You should use watch when you need to perform an action when the value of a specific reactive property changes. For example, you might use watch to update the UI when the value of a form input changes.

You should use watchEffect when you need to perform an action that depends on multiple reactive properties. For example, you might use watchEffect to calculate the total price of a product based on the quantity and unit price of the product.

In general, watchEffect is more efficient than watch because it only calls the effect function when the observed data changes. However, watch

• watch 使用立即模式反应函数 strong>，这意味着在组件安装后以及每当观察到的数据发生变化时立即调用观察者函数。
• watchEffect使用惰性模式反应函数 这意味着只有当观察到的数据发生变化时才会调用效果函数。

watch 和 watchEffect 在 Vue3 中的用法和功能有何不同？🎜🎜watch🎜 🎜watch 函数接受两个参数：🎜

1. 表示您要监视的反应性属性的字符串或字符串数​​组。
2. 一个函数，它将当观察到的属性值发生变化时执行。

rrreee🎜watchEffect🎜🎜watchEffect 函数仅接受一个参数：🎜

1. 当观察到的数据发生变化时将执行的函数。

rrreee🎜您何时以及为何选择在 Vue3 应用程序中使用 watch 或 watchEffect？🎜🎜您应该使用 watch 当您需要在特定反应性属性的值发生变化时执行操作时。例如，当表单输入的值发生变化时，您可以使用 watch 来更新 UI。🎜🎜当您需要执行依赖于以下内容的操作时，您应该使用 watchEffect多种反应特性。例如，您可以使用 watchEffect 根据商品的数量和单价来计算商品的总价。🎜🎜一般来说，watchEffect 比watch 因为它只在观察到的数据发生变化时调用效果函数。然而，watch 更简洁，更容易阅读和理解。🎜

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