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@DennyScott
DennyScott / useEffect25.js
Created March 7, 2020 08:51
function Component(props) {
useCallback(() => {
fetch(props.url);
}, [props]);
}
@DennyScott
DennyScott / useEffect24.js
Created March 7, 2020 08:51
{
name: "denny"
}
@DennyScott
DennyScott / useEffect23.js
Created March 7, 2020 08:50
function Parent() {
return(<ChildContainer name="Denny" />);
}
function Child({name}) {
return(<div>{name}</div>);
}
const mapStateToProps = state => ({...});
const mapDispatchToProps = (dispatch, ownProps) => ({...});
@DennyScott
DennyScott / useEffect22.js
Created March 7, 2020 08:49
import { fetchData } from './utils';
export function CatFacts({ id }) {
const [data, setData] = useState();
useEffect(() => {
fetchData(id, setData)
}, [id, setData]);
return <div>Cat Fact: {data}</div>;
@DennyScott
DennyScott / useEffect21.js
Created March 7, 2020 08:49
function App() {
const [index, setIndex] = useState(0);
const notMemoized = () => {
console.log("Rendered no callback");
};
const memoized = useCallback(() => console.log("Rendered callback"), []);
return (
<div className="App">
@DennyScott
DennyScott / useEffect20.js
Created March 7, 2020 08:48
export function CatFacts({ id }) {
const [data, setData] = useState();
useEffect(() => {
const proxyUrl = "https://cors-anywhere.herokuapp.com/";
const targetUrl = `https://cat-fact.herokuapp.com/facts/${id}`;
fetch(proxyUrl + targetUrl)
.then(response => response.json())
.then(facts => {
setData(facts.text);
});
@DennyScott
DennyScott / useEffect19.js
Created March 7, 2020 08:48
function ExampleComponent({url}) {
const fetchData = useCallback(() => {
// fetch call here
}, [url]);
useEffect(() => fetchData(), [fetchData]);
return (<div></div>);
}
@DennyScott
DennyScott / useEffect18.js
Created March 7, 2020 08:47
function RefEq() {
const A = () => { return 1 };
const B = A;
const C = () => { return 1 };
}
// A === B
// C !== A
@DennyScott
DennyScott / useEffect17.js
Created March 7, 2020 08:47
function eq() {
let A = 'hi';
let B = A;
let A = 'bye'
}
// A === 'bye'
// B === 'hi'
@DennyScott
DennyScott / useEffect16.js
Created March 7, 2020 08:46
function ValueEq() {
let A = 'hello';
const B = 'goodbye';
const C = 'hello';
A = 'hi';
}
// A === 'hi'
// B === 'goodbye'
// C === 'hello'