Create AppModulesConventions.md

JavaScript/AppModulesConventions.md

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+# Wikia App JavaScript modules conventions
+
+This styleguide defines the JavaScript modules strucutre conventions for Wikia App (https://github.com/Wikia/app).
+
+## TOC
+
+* [Files/directories structure](#filesdirectories-structure)
+* [Entry point files](#entry-point-files)
+* [Modules](#modules)
+* [Tracking](#tracking)
+
+
+## Files/directories structure
+
+### Keep all JS in scripts folder
+
+Keep all JavaScript files in `scripts` folder which should be located in extension's root directory (`extensions/wikia/MyExtensions/scripts`)
+
+### Entry-point files
+
+All entry points file-names should start with `index.`. If there is only one entry point file it should be named `index.js`
+
+```javascript
+// bad
+foo.js
+entry.js
+start.js
+moduleName.js
+
+// good
+index.js
+
+// good only if there are more than one entry point files
+index.example.js
+index.foo.js
+```
+
+## Entry point files
+
+### Keep them small
+
+Keep entry point files as small as possible. They should usually just execute some initialization functions from other files.
+```
+TODO: what if we want to have just one js file in extension?
+```
+
+## Modules
+
+### Name should start with extension name
+
+Each defined Modil module name should start with extension name prefix.
+
+```javascript
+// bad
+define('tracking', ['dependency'], function (dependency) {});
+
+// good
+define('MyExtensionName.tracking', ['dependency'], function (dependency) {});
+```
+
+Read more here: https://github.com/Wikia/guidelines/blob/master/JavaScript/CodingConventions.md#amd-modules
+
+### Define module as class
+
+JS module should be define as class. Currently we use ES5 so should define them using `function` keyword.
+
+```javascript
+// good
+define('MyExtensionName.tracking', ['dependency'], function (dependency) {
+  function Tracking () {
+    // constructor
+  }
+
+  Tracking.prototype.myInstanceMethod = function () {
+    // public non-static method
+  };
+
+  Tracking.myStaticFunction = function () {
+    // public static method
+  };
+
+  function _myPrivateFunction () {
+    // private function
+  }
+
+  return Tracking;
+});
+```
+
+### Private function names should start with underscore
+
+All private function should start with underscore (`_`).
+
+```javascript
+// bad
+function myPrivateFunction () {}
+
+// good
+function _myPrivateFunction () {}
+```
+
+## Tracking
+
+Keep all tracking in separated file(s). Tracking file-names should start with `tracking.`. If there is only one file that contains tracking functionality it should be named `tracking.js`.
+