Class Component Methods

React · Methods reference

React · Methods reference

📋 Overview

Legacy class component lifecycle and instance API (prefer hooks for new code).

🔧 Methods

Lifecycle methods

Method	Description
`constructor(props)`	Initialize state; bind handlers
`render()`	Return React elements (required)
`componentDidMount()`	After first paint
`componentDidUpdate(prevProps, prevState)`	After update
`componentWillUnmount()`	Cleanup before remove
`shouldComponentUpdate(nextProps, nextState)`	Return false to skip render
`getDerivedStateFromProps(props, state)`	Static — sync state from props
`getSnapshotBeforeUpdate(prevProps, prevState)`	Capture DOM before update
`componentDidCatch(error, info)`	Error boundary handler

Instance

Property / method	Description
`this.state` / `this.setState(updater, callback?)`	State read/update
`this.props`	Read-only props
`this.forceUpdate()`	Force re-render

💡 Examples

See parent topic notes for runnable snippets; this page is the complete method index.

⚠️ Pitfalls

Mutating methods return None in Python — do not chain sort() / reverse() expecting a new list.
Default JS sort() compares strings — pass (a,b) => a-b for numbers.
SQL function names differ by dialect — verify Postgres vs MySQL docs.
Django QuerySet.update() skips save() signals and auto auto_now fields on models.

Methods

React · Methods

Component API

React · Methods reference

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📋 Overview 🔧 Methods Lifecycle methods Instance 💡 Examples ⚠️ Pitfalls 🔗 Related