The watchEffect function in Vue.js is primarily used to automatically track changes in reactive states and execute side effects automatically whenever a state updates. When any reactive state referenced in watchEffect changes, Vue automatically re-executes the code within this function. This allows developers to easily respond to state changes without explicitly declaring dependencies.
For example, watchEffect can be used to perform operations synchronized with data changes, such as data validation, network requests, or complex logical computations. The main advantage of this function is that it simplifies code management by eliminating the need for manual dependency management; Vue automatically handles related dependency tracking and update scheduling.