Watchers and Deep Reactivity
React to data changes with watchers and deep watching.
What Is a Watcher?
A watcher runs a function in response to a data change.
- Unlike computed, it is for side effects
- Fetching data, logging, saving to storage
- You react when something specific changes
The watch Function
The watch function takes a source to watch and a callback that receives new and old values.
import { ref, watch } from "vue"
const query = ref("")
watch(query, (newVal, oldVal) => {
console.log("changed from", oldVal, "to", newVal)
})All lessons in this course
- Reactivity Fundamentals
- Computed Properties
- Watchers and Deep Reactivity