- Design
- Events
- States
- Side Effect
- Forms
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How would you describe the concept of "state"? A way for React to remember saved values from within a component. This is similar to declaring variables from within a component, with a few added bonuses (which we'll get to later)
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When would you want to use props instead of state? Anytime you want to pass data into a component so that component can determine what will get displayed on the screen.
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When would you want to use state instead of props? Anytime you want a component to maintain some values from within the component. (And "remember" those values even when React re-renders the component).
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What does "immutable" mean? Are props immutable? Is state immutable? Unchanging. Props are immutable. State is mutable.
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Functional State Update
- Note: if you ever need the old value of state
- to help you determine the new value of state,
- you should pass a callback function to your
- state setter function instead of using
- state directly. This callback function will
- receive the old value of state as its parameter,
- which you can then use to determine your new
- value of state.