Node.targets

<?xml version="1.0" encoding="utf-8" ?>
<Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <OutputWebroot>$(TargetDir)</OutputWebroot>
  </PropertyGroup>
  <ItemGroup>
    <gruntInputs Include="Gruntfile.js"/>
    <gruntInputs Include="app/**/*.js"/>
    <gruntInputs Include="app/**/*.html"/>
    <gruntInputs Include="content/**/*"/>
    <gruntInputs Include="index.html"/>
    <gruntOutputs Include="$(OutputWebroot)/**/*"/>
  </ItemGroup>
    
  <Target Name="npmInstall" Inputs="package.json" Outputs="node_modules" AfterTargets="BeforeBuild" BeforeTargets="CoreBuild">
    <Message Text="npm install"/>
    <Exec Command="npm --no-color install"
          CustomErrorRegularExpression="^npm ERR!"
          CustomWarningRegularExpression="^npm WARN"
          Outputs="@(npmOutputs)"
          />
    <Message Text="@(npmOutputs)"/>
  </Target>
  <Target Name="grunt" Inputs="@(gruntInputs)" Outputs="@(gruntOutputs)" AfterTargets="CoreBuild">
    <Message Text="grunt"/>
    <Exec Command="node_modules/.bin/grunt.cmd --no-color"
          EnvironmentVariables="OutputWebroot=$(OutputWebroot)"
          CustomErrorRegularExpression="^error"
          CustomWarningRegularExpression="^warning"
          Outputs="@(gruntOutputs)"
          />
    <Message Text="@(gruntOutputs)"/>
  </Target>
</Project>

Outputs takes either a string representing a single file or folder, or it takes an array. For npmInstall I only need it to watch an input file and output folder.