Run npm NodeJS scripts with Fiddler

When you have an npm script that does use a NodeJS library (through gulp for example) that does web request that you want to monitor with Fiddler, checkout this simple script!

When Fiddler is started, it uses the http://localhost:8888 by default as the proxy port. If this port is taken you will see the following message:

To see the port used by Fiddler, go to Tools –> WinINET Options... –> LAN settings –> Advanced

Now create the Powershell script fiddler-npmscript.ps1 next to your package.json file:

param(
    [string]$NpmScript = "watch", 
    [int]$ProxyPort = 8888
)

$env:https_proxy="http://localhost:$ProxyPort"
$env:http_proxy="http://localhost:$ProxyPort"
$env:NODE_TLS_REJECT_UNAUTHORIZED=0
npm run $NpmScript

This script can be called as .\fiddler-npmscript.ps1 when using the watch script with the default proxy port 8888.

When using for example the build script on port 2046 call the script as .\fiddler-npmscript.ps1 build 2046.