How to prevent visual studio 2017 from build javascript?

Simple Answer

In your csproj file, add the following line to the existing PropertyGroup block:

<PropertyGroup>
     <TypeScriptCompileBlocked>true</TypeScriptCompileBlocked>
</PropertyGroup>

If adding .ts or .tsx files to your project causes your project file to be modified, you may need to apply the following fix. See the bug report for more details.

 <ItemGroup>
      <None Remove="**/*.ts;**/*.tsx" />
      <Content Remove="**/*.ts;**/*.tsx" />
      <TypeScriptCompile Include="**/*.ts;**/*.tsx" />
 </ItemGroup>

Add a tsconfig.json file to your project root and make sure the following setting is set:

"compileOnSave": false,

Finally, Restart Visual Studio

Details

Nuget creates a generated targets file called [ProjectName].csproj.nuget.g.targets in the obj directory of your project. This targets file is importing Microsoft.NET.Sdk.Web.ProjectSystem.targets which in turn imports Microsoft.TypeScript.targets.

In the Microsoft.TypeScript.targets file, the following line has a comment that lets us know that if this property is set to true, then the TypeScript compilation task will do nothing:

<!-- Makes the TypeScript compilation task a no-op -->
<TypeScriptCompileBlocked Condition="'$(TypeScriptCompileBlocked)' == ''">false</TypeScriptCompileBlocked>