Ensure the Azure Web App has the node version you want.

1. Go to yoursite.scm.azurewebsites.net
2. Choose Debug Console (PowerShell or CMD)
3. Navigate to D:\Program Files (x86)\nodejs
4. Run dir to see the available nodejs versions.

For instance, if there is a directory named 6.3.0, then you can use it.

// App SettingWEBSITE_NODE_DEFAULT_VERSION 6.3.0  // package.jsonengines":{"node": "6.3.0"}

You can specify the version of node that the app is running on using the package.json file. Add:

"engines":{"node":version}

e.g.:

"engines":{"node": "0.12.x"}, 

More info: https://azure.microsoft.com/en-us/documentation/articles/nodejs-specify-node-version-azure-apps/

2017 update. All above didn't work for me in.

I changed:

// package.jsonengines":{"node": "8.0.0"}

and then I added app settings value

<appSettings>    <add key="WEBSITE_NODE_DEFAULT_VERSION" value="8.0.0" /></appSettings>

I restarted an app million times, and the solution was to change iisnode.yml

nodeProcessCommandLine: "D:\Program Files (x86)\nodejs\8.0.0\node.exe"

That's it. I hope it will help someone.

Update

Just to clarify things: I'm talking about App Service

And if you ftp to your App you will see iisnode.yml here: