8 Lifecycle functions

This chapters covers

  • onMount to run code when a component is added to the DOM
  • beforeUpdate to run code before every component update
  • afterUpdate to run code after every component update
  • onDestroy to run code when a component is removed from the DOM

In some applications there are actions that need to be performed when a component is added to or removed from the DOM. There are also situations where actions need to be performed before or after a component is updated. Svelte supports this by allowing the registration of functions to be invoked when four specific events occur in the lifecycle of a component instance:

  • When it is mounted (added to the DOM)

  • Before it is updated

  • After it is updated

  • When it is destroyed ...

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