Install npm in the UserProfile Folder if it does not exist.

Install-Npm.ps1

[CmdletBinding()]
param(
    [switch]$force
)

$userProfileDir = $env:USERPROFILE
$NodeDir = Join-Path $userProfileDir "Node"

if($force -and (Test-Path $NodeDir)){

    Remove-Item $NodeDir -Force -Recurse
}

$NodePath = Join-Path $NodeDir "Node.exe"
$NodeCommand = Get-Command $NodePath -ErrorAction SilentlyContinue
$NpmCommand = Get-Command "$NodeDir\npm.cmd" -ErrorAction SilentlyContinue

Function Get-ExternalTools {
    if (!$NodeCommand) {

        # External dependencies
        $sourceNodeExe = "https://nodejs.org/download/release/latest/win-x64/node.exe"


        Write-Output "Node.exe not found. Downloading to $NodePath..."
        if (!(Test-Path $NodeDir -PathType Container)) {
            New-Item -ItemType Directory -Force -Path $NodeDir | Out-Null
        }

        Invoke-WebRequest $sourceNodeExe -OutFile $NodePath
        
        $script:NodeCommand = Get-Command $NodePath        
    }

    if(!$NpmCommand){

        Write-Output "npm not found. Downloading to $NodePath..."

        $npmBaseUrl = "http://nodejs.org/dist/npm/"

        $npmZipFile = (Invoke-WebRequest $npmBaseUrl).Links | 
        Sort-Object { 
            [Version] $(if ($_.href -match "(\d+\.){3}zip") { 
                            $matches[0] -replace “.zip$”
                        } 
                        else { 
                            "0.0.0.0"
                        })  
        }  -Descending | 
        Select -Property href -First 1


        $npmLatestVersion = "$npmBaseUrl$($npmZipFile.href)"

        $npmZipPath = Join-Path $NodeDir $npmZipFile.href

        Invoke-WebRequest $npmLatestVersion -OutFile $npmZipPath

        Expand-Archive $npmZipPath -DestinationPath $NodeDir

        $script:NpmCommand = Get-Command "$NodeDir\npm.cmd"   
    }

}

Get-ExternalTools

if(!($env:Path.Contains($NodeDir))){
    Write-Output "Adding the node dir to the path environment variable"
    $env:Path += ";$NodeDir"
    [Environment]::SetEnvironmentVariable( "Path", $env:Path, [System.EnvironmentVariableTarget]::User )
}

if(!(Test-Path "$NodeDir\npm"))
{
    Write-Output "Installing npm"
    & $NpmCommand install -g npm
}