在React中加载更多按钮 步骤1：步骤2：步骤3：步骤4：

如何解决在React中加载更多按钮 步骤1：步骤2：步骤3：步骤4：

我自己找不到解决方案。我发现这个很好的教程可以解决我的问题：https://dev.to/narendersaini32/how-to-create-load-more-logic-in-react-474m，但是因为我已经有了一张地图，所以它对我不起作用！基本上，我想在链接中添加更多负载按钮，例如如何与我的解决方案结合使用，请提出任何建议，谢谢！

' Constants.
'
    ' Count of bytes/octets in a MAC48 address.
    Const OctetCount    As Integer = 6
    ' Length of a byte (octet).
    Const OctetLength   As Integer = 2
    ' Count of digits in a MAC48 address.
    Const DigitCount    As Integer = OctetCount * OctetLength
    ' Possible count of frames.
    Const FrameCount1   As Integer = 1
    Const FrameCount3   As Integer = 3
    Const FrameCount6   As Integer = 6
    ' Length of the frames in a MAC address having one,three,or six frames.
    Const FrameLength1  As Integer = DigitCount / FrameCount1
    Const FrameLength3  As Integer = DigitCount / FrameCount3
    Const FrameLength6  As Integer = DigitCount / FrameCount6
    ' Lenght of a MAC address having one,or six frames.
    Const TotalLength1  As Integer = DigitCount + FrameCount1 - 1
    Const TotalLength3  As Integer = DigitCount + FrameCount3 - 1
    Const TotalLength6  As Integer = DigitCount + FrameCount6 - 1
    ' HexPattern of one hex digit ignoring case.
    Const HexPattern    As String = "[0-9,A-Fa-f]"



' Retrieves from the local computer an array of the NICs having a MAC address.
'
' The array has four dimensions:
'   0: Byte array. MAC address of the NIC
'   1: Boolean. The NIC is IP enabled
'   2: Boolean. The NIC has been assigned a default IP gateway
'   3: String. IP address (first if several)
'   4: String. Description of the NIC.
'
' Reference:
'   https://docs.microsoft.com/en-us/windows/win32/cimwin32prov/win32-networkadapterconfiguration
'
' 2019-09-23,Cactus Data ApS,Gustav Brock
'
Public Function GetMacAddresses() As Variant()

    ' This computer.
    Const Computer      As String = "."
    ' Namespace to access the Win32_NetworkAdapterConfiguration class.
    Const NameSpace     As String = "\root\cimv2"
    ' Query to list IP enabled network adapters.
    Const Sql           As String = "Select * From Win32_NetworkAdapterConfiguration Where MACAddress Is Not Null"
    
    Dim WMIService      As Object
    Dim Adapters        As Object
    Dim Adapter         As Object
    
    Dim Octets(0 To OctetCount - 1) As Byte
    Dim Nics()          As Variant
    Dim PathName        As String
    Dim AdapterCount    As Long
    Dim Index           As Long
    
    PathName = "winmgmts:" & "{impersonationLevel=impersonate}!\\" & Computer & NameSpace
    Set WMIService = GetObject(PathName)
    
    ' Retrieve the list of network adapters having a MAC address.
    Set Adapters = WMIService.ExecQuery(Sql)
    AdapterCount = Adapters.Count
    
    If AdapterCount > 0 Then
        ' Array to hold:
        '   0: Byte array. MAC address of NIC
        '   1: Boolean. NIC is IP enabled
        '   2: Boolean. NIC has been assigned a default IP gateway
        '   3: String. IP address (first if several)
        '   4: String. NIC description
        ReDim Nics(0 To AdapterCount - 1,IpNicInformation.[_First] To IpNicInformation.[_Last])
        
        ' Loop the network adapters to fill the array.
        For Each Adapter In Adapters
            Nics(Index,IpNicInformation.ipNicMacAddress) = MacAddressParse(Adapter.MacAddress)
            Nics(Index,IpNicInformation.ipNicIpEnabled) = Adapter.IPEnabled
            Nics(Index,IpNicInformation.ipNicHasDefaultIpGateway) = Not IsNull(Adapter.DefaultIPGateway)
            If Not IsNull(Adapter.IPAddress) Then
                Nics(Index,IpNicInformation.ipNicIpAddress) = Adapter.IPAddress(0)
            End If
            Nics(Index,IpNicInformation.ipNicDescription) = Adapter.Description
            Index = Index + 1
        Next
    Else
        ' No adapter having a MAC address was found.
        ReDim Nics(0,IpNicInformation.[_First] To IpNicInformation.[_Last])
        Nics(Index,IpNicInformation.ipNicMacAddress) = Octets()
        Nics(Index,IpNicInformation.ipNicIpEnabled) = False
        Nics(Index,IpNicInformation.ipNicHasDefaultIpGateway) = False
        Nics(Index,IpNicInformation.ipNicIpAddress) = ""
        Nics(Index,IpNicInformation.ipNicDescription) = "N/A"
    End If
    
    GetMacAddresses = Nics

End Function

解决方法

您可以在本地对数据进行分页

步骤1：

首先创建一个本地索引变量，以跟踪单击“加载更多”按钮的次数。还添加页面大小和另一个状态变量以保存可见数据。

const PAGE_SIZE = 10 ;  // or whatever you like

const [index,setIndex] = useState (0)

const [visibleData,setVisibleData] = useState ([])

步骤2：

然后在加载更多按钮中添加onClick处理程序以处理索引的增加/减少

<button onClick={ () => setIndex (index+1 )}>  Load More </button>

步骤3：

然后在索引更改时添加更多数据

useEffect(() => {
    const numberOfItems = PAGE_SIZE * ( index +1 ); 

    const newArray = []; 

    for(let i= 0 ;i< portfolio.length ; i++ ){
      if(i < numberOfItems) 
          newArray.push(portfolio[i])
    }

    setVisibleData(newArray);
    
},[index])

步骤4：

现在仅渲染可见数据

    <div className="portfolio-list">
        {visibleData.map((portfolios) => {
          return <PortfolioCart key={portfolios.id} portfolios={portfolios} />;
        })}
      </div>