Excel with JavaScript

You can use Visual Studio to create an Excel Add-in project [[using Visual Studio with JavaScript]]
The link above displays the contents of these three files:

ExcelVisualStudio.xml 
Home.html 
Home.js

This page displays all the other important files in this project:

packages.config 
web.config 
Functions\FunctionFile.html 
Functions\FunctionFile.js 
Properties\AssemblyInfo.cs

packages.config

<?xml version="1.0" encoding="utf-8"?> 
<packages> 
  <package id="jQuery" version="3.4.1" targetFramework="net472" /> 
  <package id="Microsoft.CodeDom.Providers.DotNetCompilerPlatform" version="2.0.1" targetFramework="net472" /> 
  <package id="Microsoft.Office.js" version="1.1.0.17" targetFramework="net472" /> 
  <package id="OfficeUIFabricCore" version="9.6.0" targetFramework="net472" /> 
</packages>

web.config

<?xml version="1.0" encoding="utf-8"?> 
<configuration> 
  <system.web> 
    <compilation debug="true" targetFramework="4.7.2"/> 
    <httpRuntime targetFramework="4.7.2"/> 
  </system.web> 
  <system.codedom> 
    <compilers> 
      <compiler language="c#;cs;csharp" extension=".cs" 
        type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, 
           Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=2.0.1.0, 
           Culture=neutral, PublicKeyToken=31bf3856ad364e35" 
        warningLevel="4" compilerOptions="/langversion:default /nowarn:1659;1699;1701"/> 
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" 
        type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, 
           Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=2.0.1.0, 
           Culture=neutral, PublicKeyToken=31bf3856ad364e35" 
        warningLevel="4" compilerOptions="/langversion:default /nowarn:41008 /define:_MYTYPE=\"Web\" /optionInfer+"/> 
    </compilers> 
  </system.codedom> 
</configuration>

FunctionFile.html

<!DOCTYPE html> 
<html> 
<head> 
    <meta charset="UTF-8" /> 
    <meta http-equiv="X-UA-Compatible" content="IE=Edge" /> 
    <title></title> 
    <script src="https://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.9.1.min.js" type="text/javascript"></script> 
    <script src="https://appsforoffice.microsoft.com/lib/1/hosted/office.js" type="text/javascript"></script> 
    <script src="FunctionFile.js" type="text/javascript"></script> 
</head> 
<body> 
</body> 
</html>

FunctionFile.js

(function () { 
    Office.initialize = function (reason) { 
        // If you need to initialize something you can do so here. 
    }; 
})();

AssemblyInfo.cs

using System.Reflection; 
using System.Runtime.CompilerServices; 
using System.Runtime.InteropServices; 

[assembly: AssemblyTitle("ExcelVisualStudioWeb")] 
[assembly: AssemblyDescription("")] 
[assembly: AssemblyConfiguration("")] 
[assembly: AssemblyCompany("")] 
[assembly: AssemblyProduct("ExcelVisualStudioWeb")] 
[assembly: AssemblyCopyright("Copyright")] 
[assembly: AssemblyTrademark("")] 
[assembly: AssemblyCulture("")] 
[assembly: ComVisible(false)] 
[assembly: Guid("51c72263-9b09-41f5-8363-4508b4670f0e")] 
[assembly: AssemblyVersion("1.0.0.0")] 
[assembly: AssemblyFileVersion("1.0.0.0")]