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React Lifecycle


React.Component Lifecycle

https://twitter.com/dan_abramov/status/981712092611989509

React Hooks Lifecycle

https://github.com/Wavez/react-hooks-lifecycle

React Hook flow

https://github.com/donavon/hook-flow
const Child = () => {
console.log("%c Child: render 시작", "color: MediumSpringGreen");

const [count, setCount] = useState(() => {
console.log("%c Child: useState callback 호출", "color: tomato");
return 0;
});

useEffect(() => {
console.log("%c Child: useEffect - deps 없음", "color: LightCoral");
return () => {
console.log(
"%c Child: useEffect cleanup - deps 없음",
"color: LightCoral"
);
};
});

useEffect(() => {
console.log("%c Child: useEffect - deps [] ", "color: MediumTurquoise");
return () => {
console.log(
"%c Child: useEffect cleanup - deps []",
"color: MediumTurquoise"
);
};
}, []);

useEffect(() => {
console.log("%c Child: useEffect - deps [count]", "color: HotPink");
return () => {
console.log(
"%c Child: useEffect cleanup - deps [count]",
"color: HotPink"
);
};
}, [count]);

const element = (
<button onClick={() => setCount((previousCount) => previousCount + 1)}>
{count}
</button>
);

console.log("%c Child: render 끝", "color: MediumSpringGreen");

return element;
};

const App = () => {
console.log("%cApp: render 시작", "color: MediumSpringGreen");

const [showChild, setShowChild] = useState(() => {
console.log("%cApp: useState callback 호출", "color: tomato");
return false;
});

useEffect(() => {
console.log("%cApp: useEffect - deps 없음", "color: LightCoral");
return () => {
console.log("%cApp: useEffect cleanup - deps 없음", "color: LightCoral");
};
});

useEffect(() => {
console.log("%cApp: useEffect - deps []", "color: MediumTurquoise");
return () => {
console.log(
"%cApp: useEffect cleanup - deps []",
"color: MediumTurquoise"
);
};
}, []);

useEffect(() => {
console.log("%cApp: useEffect - deps [showChild]", "color: HotPink");
return () => {
console.log(
"%cApp: useEffect cleanup - deps [showChild]",
"color: HotPink"
);
};
}, [showChild]);

const element = (
<>
<label>
<input
type="checkbox"
checked={showChild}
onChange={(e) => setShowChild(e.target.checked)}
/>{" "}
Child 보기
</label>
<div
style={{
padding: 10,
margin: 10,
height: 30,
width: 30,
border: "solid",
}}
>
{showChild ? <Child /> : null}
</div>
</>
);

console.log("%cApp: render 끝", "color: MediumSpringGreen");

return element;
};

페이지 진입

App: render 시작
App: useState callback 호출
App: render 끝
App: useEffect - deps 없음
App: useEffect - deps []
App: useEffect - deps [showChild]

Child 보기 체크박스 on

App: render 시작
App: render 끝
Child: render 시작
Child: useState callback 호출
Child: render 끝
Child: useEffect - deps 없음
Child: useEffect - deps []
Child: useEffect - deps [count]
App: useEffect cleanup - deps 없음
App: useEffect cleanup - deps [showChild]
App: useEffect - deps 없음
App: useEffect - deps [showChild]

Child의 Count 버튼 클릭

    Child: render 시작
Child: render 끝
Child: useEffect cleanup - deps 없음
Child: useEffect cleanup - deps [count]
Child: useEffect - deps 없음
Child: useEffect - deps [count]

Child 보기 체크박스 off

App: render 시작
App: render 끝
Child: useEffect cleanup - deps 없음
Child: useEffect cleanup - deps []
Child: useEffect cleanup - deps [count]
App: useEffect cleanup - deps 없음
App: useEffect cleanup - deps [showChild]
App: useEffect - deps 없음
App: useEffect - deps [showChild]