Faqs

https://youtu.be/9mFX2Iy3dMU

https://github.com/testing-library/react-hooks-testing-library useCounter.js import { useState , useCallback } from ' react ' function useCounter () { const [ count , setCount ] = useState ( 0 ) const increment = useCallback (() => setCount (( x ) => x + 1 ), []) return { count, increment } } export default useCounter useCounter.test.js import { renderHook , act } from ' @testing-library/react-hooks ' import useCounter from ' ./useCounter ' test ( ' should increment counter ' , () => { const { result } = renderHook (() => useCounter ()) act (() => { result . current . increment () }) expect ( result . current . count ). toBe ( 1 ) })

https://wanago.io/2019/12/09/javascript-design-patterns-facade-react-hooks/ function useUsersManagement ( ) {    const [ users , setUsers ] = useState ( [ ] ) ;      function addUser ( user ) {      setUsers ( [        . . . users ,        user      ] )    }      function deleteUser ( userId ) {      const userIndex = users . findIndex ( user = > user . id === userId ) ;      if ( userIndex > - 1 ) {        const newUsers = [ . . . users ] ;        newUsers . splice ( userIndex , 1 ) ;        setUsers (          newUsers        ) ;      }    }      return {      users ,      addUser ,      deleteUser    } }

https://github.com/Urigo/graphql-scalars scalar DateTime scalar EmailAddress scalar NegativeFloat scalar NegativeInt scalar NonNegativeFloat scalar NonNegativeInt scalar NonPositiveFloat scalar NonPositiveInt scalar PhoneNumber scalar PositiveFloat scalar PositiveInt scalar PostalCode scalar UnsignedFloat scalar UnsignedInt scalar URL scalar ObjectID scalar BigInt scalar Long scalar GUID scalar HexColorCode scalar HSL scalar HSLA scalar IPv4 scalar IPv6 scalar ISBN scalar MAC scalar Port scalar RGB scalar RGBA scalar USCurrency scalar JSON scalar JSONObject

http://learnjsdata.com/iterate_data.html var landSum = data.reduce( (sum, d)=> sum + d.land_area, 0 ); console .log(landSum); var weirdString = data.reduce( function (str, d, i) { var ending = (i % 2 === 0 ) ? " is cool." : " sucks." ; return str.concat( " " , d.city , ending) }, "" ); console .log(weirdString);