@Baranidharan R Thanks for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.
As per the Angular official documentation, we see that v4.2 is one of the unsupported version which needs underlying NodeJS of version ^6.9.0 .
Currently below are the list of Nodejs versions which are supported in the app service.
I would suggest you try upgrading your application to latest version of angular and deploy it to the respective supported NodeJs runtime on app service.
You can also refer to the below documentation on deploying angular applications to app service.
- Angular Deployment on App Service Linux
- Creating an AngularJS Single Page Application with routes on Azure WebApps
Hope this helps. Let me know if you have any further questions on this.