Callback Methods in Lightning Web Components(lwc)

Callback methods are triggered at a specific phase of a component instance lifecycle.

Callback Methods in Lighting Web Components(lwc)

1. constructor()
2. connectedCallback()
3. disconnectedCallback()
4. render()
5. renderedCallback()
6. errorCallback(error, stack)

constructor()

• This callback method called when the component created.
• This method lifecycle flows from Parent to Child component.
• You can access the host element with this.template.
• we can’t access child elements in the component body because they don’t exist yet.

connectedCallback()

• This callback method called when the element is inserted into a document.
• This method lifecycle flows from Parent to Child Component.
• we can’t access child elements in the component body because they don’t exist yet.
• You can access the host element with this.template.

disconnectedCallback()

• This callback method called when the element is removed from a document.
• This method lifecycle flows from Parent to Child Component.

render()

• This callback method used to conditionally rendering a template or importing a custom one, use render() to override standard rendering functionality. 
• This function gets invoked after connectedCallback() and must return a valid HTML template.

renderedCallback()

• This Method called after every render of the component.
• This callback method is specific to Lightning Web Components, it isn’t from the HTML custom elements specification.
• This method flows from child to parent.

 errorCallback(error, stack)

• This method called when a descendant component throws an error in one of its callback.
•  The error argument is a JavaScript native error object, and the stack argument is a string.
•  This callback method is specific to Lightning Web Components, it isn’t from the HTML custom elements specification.

Resource
Callback methods in Lightning Web Components