When you remove a module manually or re import a database, some times you have a message like "The following module is missing from the file system...". this is due to deleted modules.
Note : On drupal the best practice is use drupal behaviors but not JS or Jquery codes such as:
Drupal's event system allow to create triggers when an event has been happened like create a custom hook on drupal 7.
To get database table columns names of a mysql database you can use "DESCRIBE my_table;" method.
CAUTION : At this day (2017-10-12), Drupal commerce is very young. Therefor you can start the development of your e-commerce site but you may have bugs and security issues.
Example 1 (for drupal 7)
Step 1. Add file brows
Disable cache for a custom page from route declaration.
If you want to disable cache for a custom controller (Custom module), You have no_cache option (YOUR_MODULE.routing.yml).
File : mymodule.routing.yml
This is a simple example of a web service. For the example, We will make a service to multiply two numbers.
Create JSON WebService module
Create a module.
Here : mywebservice
Create a Drupal 8 module is a good idea, but develop as Drupal is BEST.
The famous tools PhpCS and PhpCBF allow you to check and correct (some) drupal coding standards and best practice errors.