Update AsyncStorage doc

Summary:
Relates to #8203 for AsyncStorage API update.

- Added a small example to the intro section.
- Added jsdoc format tags to show up class description, parameter descriptions.
- Word-smithed many of the method descriptions.

I also made a bug fix to the autogen. It wasn't handling the scenario where a method may have no parameters.

**Test plan (required)**

Wrote a small sample app to test the snippet added to the intro section.

Ran website locally: http://localhost:8079/react-native/docs/asyncstorage.html

![api_asyncstorage](https://cloud.githubusercontent.com/assets/691109/16329457/84f9d69c-3997-11e6-9e68-3a475df90377.png)

Ran changed files through the linter.
Closes #8396

Differential Revision: D3481783

Pulled By: JoelMarcey

fbshipit-source-id: ebc4b9695482ada8a3455e621534d2a7fb11edf4

Author: Christine Abernathy

Libraries/Storage/AsyncStorage.js

@@ -9,6 +9,7 @@
  * @providesModule AsyncStorage
  * @noflow
  * @flow-weak
+ * @jsdoc
  */
 'use strict';
 
@@ -21,27 +22,58 @@ var RCTAsyncFileStorage = NativeModules.AsyncLocalStorage;
 var RCTAsyncStorage = RCTAsyncRocksDBStorage || RCTAsyncSQLiteStorage || RCTAsyncFileStorage;
 
 /**
- * AsyncStorage is a simple, asynchronous, persistent, key-value storage
+ * @class
+ * @description
+ * `AsyncStorage` is a simple, asynchronous, persistent, key-value storage
  * system that is global to the app.  It should be used instead of LocalStorage.
  *
- * It is recommended that you use an abstraction on top of AsyncStorage instead
- * of AsyncStorage directly for anything more than light usage since it
- * operates globally.
+ * It is recommended that you use an abstraction on top of `AsyncStorage`
+ * instead of `AsyncStorage` directly for anything more than light usage since
+ * it operates globally.
  *
- * On iOS, AsyncStorage is backed by native code that stores small values in a serialized
- * dictionary and larger values in separate files. On Android, AsyncStorage will use either
- * RocksDB or SQLite based on what is available. This JS code is a simple facade that
- * provides a clear JS API, real Error objects, and simple non-multi functions. Each
- * method returns a `Promise` object.
+ * On iOS, `AsyncStorage` is backed by native code that stores small values in a
+ * serialized dictionary and larger values in separate files. On Android,
+ * `AsyncStorage` will use either [RocksDB](http://rocksdb.org/) or SQLite
+ * based on what is available.
+ *
+ * The `AsyncStorage` JavaScript code is a simple facade that provides a clear
+ * JavaScript API, real `Error` objects, and simple non-multi functions. Each
+ * method in the API returns a `Promise` object.
+ *
+ * Persisting data:
+ * ```
+ * try {
+ *   await AsyncStorage.setItem('@MySuperStore:key', 'I like to save it.');
+ * } catch (error) {
+ *   // Error saving data
+ * }
+ * ```
+ *
+ * Fetching data:
+ * ```
+ * try {
+ *   const value = await AsyncStorage.getItem('@MySuperStore:key');
+ *   if (value !== null){
+ *     // We have data!!
+ *     console.log(value);
+ *   }
+ * } catch (error) {
+ *   // Error retrieving data
+ * }
+ * ```
  */
 var AsyncStorage = {
   _getRequests: ([]: Array<any>),
   _getKeys: ([]: Array<string>),
   _immediate: (null: ?number),
 
   /**
-   * Fetches `key` and passes the result to `callback`, along with an `Error` if
-   * there is any. Returns a `Promise` object.
+   * Fetches an item for a `key` and invokes a callback upon completion.
+   * Returns a `Promise` object.
+   * @param key Key of the item to fetch.
+   * @param callback Function that will be called with a result if found or
+   *    any error.
+   * @returns A `Promise` object.
    */
   getItem: function(
     key: string,
@@ -63,8 +95,12 @@ var AsyncStorage = {
   },
 
   /**
-   * Sets `value` for `key` and calls `callback` on completion, along with an
-   * `Error` if there is any. Returns a `Promise` object.
+   * Sets the value for a `key` and invokes a callback upon completion.
+   * Returns a `Promise` object.
+   * @param key Key of the item to set.
+   * @param value Value to set for the `key`.
+   * @param callback Function that will be called with any error.
+   * @returns A `Promise` object.
    */
   setItem: function(
     key: string,
@@ -85,7 +121,11 @@ var AsyncStorage = {
   },
 
   /**
+   * Removes an item for a `key` and invokes a callback upon completion.
    * Returns a `Promise` object.
+   * @param key Key of the item to remove.
+   * @param callback Function that will be called with any error.
+   * @returns A `Promise` object.
    */
   removeItem: function(
     key: string,
@@ -105,32 +145,39 @@ var AsyncStorage = {
   },
 
   /**
-   * Merges existing value with input value, assuming they are stringified json.
-   * Returns a `Promise` object. Not supported by all native implementations.
+   * Merges an existing `key` value with an input value, assuming both values
+   * are stringified JSON. Returns a `Promise` object.
    *
-   * Example:
-   * ```javascript
+   * **NOTE:** This is not supported by all native implementations.
+   *
+   * @param key Key of the item to modify.
+   * @param value New value to merge for the `key`.
+   * @param callback Function that will be called with any error.
+   * @returns A `Promise` object.
+   *
+   * @example <caption>Example</caption>
    * let UID123_object = {
    *  name: 'Chris',
    *  age: 30,
    *  traits: {hair: 'brown', eyes: 'brown'},
    * };
-
-   // need only define what will be added or updated
+   * // You only need to define what will be added or updated
    * let UID123_delta = {
    *  age: 31,
    *  traits: {eyes: 'blue', shoe_size: 10}
    * };
-
+   *
    * AsyncStorage.setItem('UID123', JSON.stringify(UID123_object), () => {
    *   AsyncStorage.mergeItem('UID123', JSON.stringify(UID123_delta), () => {
    *     AsyncStorage.getItem('UID123', (err, result) => {
    *       console.log(result);
-   *       // => {'name':'Chris','age':31,'traits':{'shoe_size':10,'hair':'brown','eyes':'blue'}}
    *     });
    *   });
    * });
-   * ```
+   *
+   * // Console log result:
+   * // => {'name':'Chris','age':31,'traits':
+   * //    {'shoe_size':10,'hair':'brown','eyes':'blue'}}
    */
   mergeItem: function(
     key: string,
@@ -151,9 +198,11 @@ var AsyncStorage = {
   },
 
   /**
-   * Erases *all* AsyncStorage for all clients, libraries, etc.  You probably
-   * don't want to call this - use removeItem or multiRemove to clear only your
-   * own keys instead. Returns a `Promise` object.
+   * Erases *all* `AsyncStorage` for all clients, libraries, etc.  You probably
+   * don't want to call this; use `removeItem` or `multiRemove` to clear only
+   * your app's keys. Returns a `Promise` object.
+   * @param callback Function that will be called with any error.
+   * @returns A `Promise` object.
    */
   clear: function(callback?: ?(error: ?Error) => void): Promise {
     return new Promise((resolve, reject) => {
@@ -169,9 +218,12 @@ var AsyncStorage = {
   },
 
   /**
-   * Gets *all* keys known to the app, for all callers, libraries, etc. Returns a `Promise` object.
+   * Gets *all* keys known to your app; for all callers, libraries, etc.
+   * Returns a `Promise` object.
+   * @param callback Function that will be called the keys found and any error.
+   * @returns A `Promise` object.
    *
-   * Example: see multiGet for example
+   * Example: see the `multiGet` example.
    */
   getAllKeys: function(callback?: ?(error: ?Error, keys: ?Array<string>) => void): Promise {
     return new Promise((resolve, reject) => {
@@ -196,7 +248,7 @@ var AsyncStorage = {
    * indicate which key caused the error.
    */
 
-  /** Flushes any pending requests using a single multiget */
+  /** Flushes any pending requests using a single batch call to get the data. */
   flushGetRequests: function(): void {
     const getRequests = this._getRequests;
     const getKeys = this._getKeys;
@@ -225,13 +277,23 @@ var AsyncStorage = {
   },
 
   /**
-   * multiGet invokes callback with an array of key-value pair arrays that
-   * matches the input format of multiSet. Returns a `Promise` object.
+   * This allows you to batch the fetching of items given an array of `key`
+   * inputs. Your callback will be invoked with an array of corresponding
+   * key-value pairs found:
    *
-   *   multiGet(['k1', 'k2'], cb) -> cb([['k1', 'val1'], ['k2', 'val2']])
+   * ```
+   * multiGet(['k1', 'k2'], cb) -> cb([['k1', 'val1'], ['k2', 'val2']])
+   * ```
+   *
+   * The method returns a `Promise` object.
+   *
+   * @param keys Array of key for the items to get.
+   * @param callback Function that will be called with a key-value array of
+   *     the results, plus an array of any key-specific errors found.
+   * @returns A `Promise` object.
+   *
+   * @example <caption>Example</caption>
    *
-   * Example:
-   * ```javascript
    * AsyncStorage.getAllKeys((err, keys) => {
    *   AsyncStorage.multiGet(keys, (err, stores) => {
    *    stores.map((result, i, store) => {
@@ -241,7 +303,6 @@ var AsyncStorage = {
    *     });
    *   });
    * });
-   * ```
    */
   multiGet: function(
     keys: Array<string>,
@@ -280,12 +341,20 @@ var AsyncStorage = {
   },
 
   /**
-   * multiSet and multiMerge take arrays of key-value array pairs that match
-   * the output of multiGet, e.g. Returns a `Promise` object.
+   * Use this as a batch operation for storing multiple key-value pairs. When
+   * the operation completes you'll get a single callback with any errors:
    *
-   *   multiSet([['k1', 'val1'], ['k2', 'val2']], cb);
+   * ```
+   * multiSet([['k1', 'val1'], ['k2', 'val2']], cb);
+   * ```
+   *
+   * The method returns a `Promise` object.
    *
-   * Example: see multiMerge for an example
+   * @param keyValuePairs Array of key-value array for the items to set.
+   * @param callback Function that will be called with an array of any
+   *    key-specific errors found.
+   * @returns A `Promise` object.
+   * Example: see the `multiMerge` example.
    */
   multiSet: function(
     keyValuePairs: Array<Array<string>>,
@@ -305,16 +374,20 @@ var AsyncStorage = {
   },
 
   /**
-   * Delete all the keys in the `keys` array. Returns a `Promise` object.
+   * Call this to batch the deletion of all keys in the `keys` array. Returns
+   * a `Promise` object.
    *
-   * Example:
-   * ```javascript
+   * @param keys Array of key for the items to delete.
+   * @param callback Function that will be called an array of any key-specific
+   *    errors found.
+   * @returns A `Promise` object.
+   *
+   * @example <caption>Example</caption>
    * let keys = ['k1', 'k2'];
    * AsyncStorage.multiRemove(keys, (err) => {
    *   // keys k1 & k2 removed, if they existed
    *   // do most stuff after removal (if you want)
    * });
-   * ```
    */
   multiRemove: function(
     keys: Array<string>,
@@ -334,56 +407,62 @@ var AsyncStorage = {
   },
 
   /**
-   * Merges existing values with input values, assuming they are stringified
-   * json. Returns a `Promise` object.
+   * Batch operation to merge in existing and new values for a given set of
+   * keys. This assumes that the values are stringified JSON. Returns a
+   * `Promise` object.
    *
-   * Not supported by all native implementations.
+   * **NOTE**: This is not supported by all native implementations.
    *
-   * Example:
-   * ```javascript
-   // first user, initial values
+   * @param keyValuePairs Array of key-value array for the items to merge.
+   * @param callback Function that will be called with an array of any
+   *    key-specific errors found.
+   * @returns A `Promise` object.
+   *
+   * @example <caption>Example</caption>
+   * // first user, initial values
    * let UID234_object = {
    *  name: 'Chris',
    *  age: 30,
    *  traits: {hair: 'brown', eyes: 'brown'},
    * };
-
+   *
    * // first user, delta values
    * let UID234_delta = {
    *  age: 31,
    *  traits: {eyes: 'blue', shoe_size: 10},
    * };
-
+   *
    * // second user, initial values
    * let UID345_object = {
    *  name: 'Marge',
    *  age: 25,
    *  traits: {hair: 'blonde', eyes: 'blue'},
    * };
-
+   *
    * // second user, delta values
    * let UID345_delta = {
    *  age: 26,
    *  traits: {eyes: 'green', shoe_size: 6},
    * };
-
+   *
    * let multi_set_pairs   = [['UID234', JSON.stringify(UID234_object)], ['UID345', JSON.stringify(UID345_object)]]
    * let multi_merge_pairs = [['UID234', JSON.stringify(UID234_delta)], ['UID345', JSON.stringify(UID345_delta)]]
-
+   *
    * AsyncStorage.multiSet(multi_set_pairs, (err) => {
    *   AsyncStorage.multiMerge(multi_merge_pairs, (err) => {
    *     AsyncStorage.multiGet(['UID234','UID345'], (err, stores) => {
    *       stores.map( (result, i, store) => {
    *         let key = store[i][0];
    *         let val = store[i][1];
    *         console.log(key, val);
-   *         // => UID234 {"name":"Chris","age":31,"traits":{"shoe_size":10,"hair":"brown","eyes":"blue"}}
-   *         // => UID345 {"name":"Marge","age":26,"traits":{"shoe_size":6,"hair":"blonde","eyes":"green"}}
    *       });
    *     });
    *   });
    * });
-   * ```
+   *
+   * // Console log results:
+   * // => UID234 {"name":"Chris","age":31,"traits":{"shoe_size":10,"hair":"brown","eyes":"blue"}}
+   * // => UID345 {"name":"Marge","age":26,"traits":{"shoe_size":6,"hair":"blonde","eyes":"green"}}
    */
   multiMerge: function(
     keyValuePairs: Array<Array<string>>,

website/layout/AutodocsLayout.js

@@ -650,7 +650,7 @@ var Method = React.createClass({
           </span> || ''}
           {this.props.name}
           <span className="propType">
-            ({this.props.params
+            ({this.props.params && this.props.params.length && this.props.params
               .map((param) => {
                 var res = param.name;
                 res += param.optional ? '?' : '';