How to connect external camera to iPhone and take/

I want to connect an external camera to an iPhone (the camera built into the iPhone is inadequate for my needs) and then write an iPhone app that allows me to send a signal to the external camera when I desire to take a picture and then immediately download the taken photo onto my iPhone so that I can send it wirelessly to a server somewhere else.

I have a lot of experience with web programming and JS, but I have no experience with iPhone apps, and I'm not sure if what I want to do is even possible. Ideally, if I could get away with coding this in JS and then using Cordova (or something similar) to make an app that can run on any iDevice or Android device, that would be great.

However, assuming that that is not possible, I would like to focus on an app for just iDevices at first. I looked around the web for resources on this subject, but I couldn't find anything.

I have two questions:

Is what I want to do even possible?
If so, can I do it by using web technologies and then something like Cordova and/or a Chrome App to convert it to something that can be used on any smart device? If not, what are some good books/resources for learning how to do this on an iPhone?

Even though I've never coded an iPhone app before, I'm more than happy to try to learn, but I need some books/resources that explain everything from the basics of how to create a "Hello, World!" iPhone app to the point that I can do all the things listed above.

Thank you very much.

Answer to your first question is Yes But all this is not very straight forward. Let me explain it how this can be done But I am not sure if that will be feasible solution for you.

You can attach your external accessories to iPhone via cable (lighting connector now a days for iPhone 5 and later and with old 30 pin connector earlier devices) or via Wifi (Bluetooth ). If you connect via cable or Bluetooth (Classic) you need to signup with apple for MFI . That process apple have make it difficult and now only companies can sign for that.
After you signup you need to use MFI chip in your device (camera) to communicate with it . You can use ExternalAccessory Framework for your development after you done with the above.
Another solution is Bluetooth Low Energy (BLE) for this you don't need to signup with apple you can just enable your device with BLE and start developing your app using CoreBluetooth framework . But BLE data transfer rate is very low so may not be good enough for photos transfer.

And answer to your 2nd question is may it is possible if you can use CoreBluetooth or ExternalAccessory Framework with Cordova or any other platform you want to use.