React and Node.js on Azure App Service/IIS

web.config

<configuration>
  <system.webServer>

    <handlers>
      <add name="iisnode" path="server/server.js" verb="*" modules="iisnode" />
    </handlers>

    <rewrite>
      <rules>
        <rule name="Static Assets" stopProcessing="true">
          <match url="([\S]+[.](html|htm|svg|js|css|png|gif|jpg|jpeg))" />
          <action type="Rewrite" url="client/build/{R:1}"/>
        </rule>

        <rule name="Index" stopProcessing="true">
          <match url="^$" />
          <action type="Rewrite" url="client/build/index.html"/>
        </rule>

        <rule name="React Routes" stopProcessing="true">
          <match url=".*" />
          <conditions logicalGrouping="MatchAll">
            <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true" />
            <add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true" />
            <add input="{REQUEST_URI}" pattern="api/" negate="true" />
          </conditions>
          <action type="Rewrite" url="client/build/index.html"  />
        </rule>

        <rule name="API">
          <conditions>
            <add input="{REQUEST_FILENAME}" matchType="IsFile" negate="True"/>
          </conditions>
          <action type="Rewrite" url="server/server.js"/>
        </rule>
      </rules>
    </rewrite>

  </system.webServer>
</configuration>