Heim >Web-Frontend >View.js >Der Unterschied und die Verwendung zwischen watch und watchEffect in Vue3
The article explores the differences between watch and watchEffect in Vue 3, highlighting their usage and functionality. watch is an immediate mode reactive function, called upon component mounting and data changes, while watchEffect is a lazy mode r
Vue3 introduces a new reactivity API that includes two new functions: 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.watch
The watch
function accepts two arguments:
<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:
<code>watchEffect(() => { console.log(`The count is now ${count}`); });</code>
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
is more concise and easier to read and understand.
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