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450What Makes a Component 'Controlled'
451The value Prop on Inputs
452The onChange Handler
453The Basic Pattern: useState + value + onChange
454Accessing Input Values: event.target.value
455Controlled Text Inputs
456Controlled Textareas
457Controlled Select Dropdowns
458Controlled Checkboxes
459Controlled Radio Buttons
460Multi-Select Dropdowns
461The Cursor Jump Problem
462Why Controlled Components Re-render on Every Change
463What 'Single Source of Truth' Means
464The Two-State Problem in Uncontrolled Inputs
465Controlled: State Drives the DOM
466Why onChange is Required with value
467The setState → Re-render → DOM Update Flow
468Benefits: Validation and Formatting On-the-Fly
469Benefits: Conditional Rendering Based on Input
470Benefits: Resetting Inputs Programmatically
471Tradeoff: Extra Re-renders
472Every Keystroke Triggers a Re-render
473Measuring the Actual Performance Impact
474When Re-render Cost Becomes a Problem
475The Parent Component Re-render Chain
476Mitigating Cost: Lift State Down
477Mitigating Cost: Debouncing State Updates
478When Uncontrolled is the Better Choice
479Modern Solutions: React Hook Form's Performance
480The Standard Controlled Input Pattern
481Text Input: value and onChange
482Textarea: Same Pattern, Different Element
483Checkbox: checked and onChange
484Radio Buttons: Grouping by name
485Select Dropdown: value on the select Element
486Multi-Select: value as Array
487Number Input: Parsing and Validation
488Generic onChange Handler Pattern
489Controlled Input Recipe Reference

450What Makes a Component 'Controlled'
451The value Prop on Inputs
452The onChange Handler
453The Basic Pattern: useState + value + onChange
454Accessing Input Values: event.target.value
455Controlled Text Inputs
456Controlled Textareas
457Controlled Select Dropdowns
458Controlled Checkboxes
459Controlled Radio Buttons
460Multi-Select Dropdowns
461The Cursor Jump Problem
462Why Controlled Components Re-render on Every Change
463What 'Single Source of Truth' Means
464The Two-State Problem in Uncontrolled Inputs
465Controlled: State Drives the DOM
466Why onChange is Required with value
467The setState → Re-render → DOM Update Flow
468Benefits: Validation and Formatting On-the-Fly
469Benefits: Conditional Rendering Based on Input
470Benefits: Resetting Inputs Programmatically
471Tradeoff: Extra Re-renders
472Every Keystroke Triggers a Re-render
473Measuring the Actual Performance Impact
474When Re-render Cost Becomes a Problem
475The Parent Component Re-render Chain
476Mitigating Cost: Lift State Down
477Mitigating Cost: Debouncing State Updates
478When Uncontrolled is the Better Choice
479Modern Solutions: React Hook Form's Performance
480The Standard Controlled Input Pattern
481Text Input: value and onChange
482Textarea: Same Pattern, Different Element
483Checkbox: checked and onChange
484Radio Buttons: Grouping by name
485Select Dropdown: value on the select Element
486Multi-Select: value as Array
487Number Input: Parsing and Validation
488Generic onChange Handler Pattern
489Controlled Input Recipe Reference

Lesson 452 of 2,396·13. Controlled ComponentsPro lesson

The onChange Handler

onChange fires on every keystroke, updating state and allowing the component to re-render with the new value.

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