diff --git a/lib/cursor.js b/lib/cursor.js
index 603b844..0882d88 100755
--- a/lib/cursor.js
+++ b/lib/cursor.js
@@ -33,10 +33,16 @@ class Cursor {
     this.query = query || {}
     if (execFn) this.execFn = execFn
     if (async) this.async = true
+    this._limit = null
+    this._skip = null
+    this._sort = null
+    this._projection = null
   }
 
   /**
    * Set a limit to the number of results
+   * @param {Number} limit
+   * @return {Cursor}
    */
   limit (limit) {
     this._limit = limit
@@ -44,7 +50,9 @@ class Cursor {
   }
 
   /**
-   * Skip a the number of results
+   * Skip a number of results
+   * @param {Number} skip
+   * @return {Cursor}
    */
   skip (skip) {
     this._skip = skip
@@ -53,7 +61,8 @@ class Cursor {
 
   /**
    * Sort results of the query
-   * @param {SortQuery} sortQuery - SortQuery is { field: order }, field can use the dot-notation, order is 1 for ascending and -1 for descending
+   * @param {Object.<string, number>} sortQuery - sortQuery is { field: order }, field can use the dot-notation, order is 1 for ascending and -1 for descending
+   * @return {Cursor}
    */
   sort (sortQuery) {
     this._sort = sortQuery
@@ -62,8 +71,9 @@ class Cursor {
 
   /**
    * Add the use of a projection
-   * @param {Object} projection - MongoDB-style projection. {} means take all fields. Then it's { key1: 1, key2: 1 } to take only key1 and key2
-   *                              { key1: 0, key2: 0 } to omit only key1 and key2. Except _id, you can't mix takes and omits
+   * @param {Object.<string, number>} projection - MongoDB-style projection. {} means take all fields. Then it's { key1: 1, key2: 1 } to take only key1 and key2
+   * { key1: 0, key2: 0 } to omit only key1 and key2. Except _id, you can't mix takes and omits.
+   * @return {Cursor}
    */
   projection (projection) {
     this._projection = projection
@@ -72,6 +82,8 @@ class Cursor {
 
   /**
    * Apply the projection
+   * @param {document[]} candidates
+   * @return {document[]}
    */
   project (candidates) {
     const res = []
@@ -118,9 +130,8 @@ class Cursor {
   /**
    * Get all matching elements
    * Will return pointers to matched elements (shallow copies), returning full copies is the role of find or findOne
-   * This is an internal function, use exec which uses the executor
-   *
-   * @param {Function} callback - Signature: err, results
+   * This is an internal function, use execAsync which uses the executor
+   * @return {document[]|Promise<*>}
    */
   async _execAsync () {
     let res = []
@@ -180,16 +191,39 @@ class Cursor {
     else return res
   }
 
+  /**
+   * @callback Cursor~execCallback
+   * @param {Error} err
+   * @param {document[]|*} res If an execFn was given to the Cursor, then the type of this parameter is the one returned by the execFn.
+   */
+
+  /**
+   * Get all matching elements
+   * Will return pointers to matched elements (shallow copies), returning full copies is the role of find or findOne
+   * This is an internal function, use exec which uses the executor
+   * @param { Cursor~execCallback} _callback
+   */
   _exec (_callback) {
     callbackify(this._execAsync.bind(this))(_callback)
   }
 
-  exec (...args) {
-    this.db.executor.push({ this: this, fn: this._exec, arguments: args })
+  /**
+   * Get all matching elements
+   * Will return pointers to matched elements (shallow copies), returning full copies is the role of find or findOne
+   * @param { Cursor~execCallback} _callback
+   */
+  exec (_callback) {
+    this.db.executor.push({ this: this, fn: this._exec, arguments: [_callback] })
   }
 
-  execAsync (...args) {
-    return this.db.executor.pushAsync(() => this._execAsync(...args))
+  /**
+   * Get all matching elements
+   * Will return pointers to matched elements (shallow copies), returning full copies is the role of find or findOne
+   * @return {Promise<document[]|*>}
+   * @async
+   */
+  execAsync () {
+    return this.db.executor.pushAsync(() => this._execAsync())
   }
 
   then (onFulfilled, onRejected) {
diff --git a/lib/customUtils.js b/lib/customUtils.js
index da538e7..a3fc1f0 100755
--- a/lib/customUtils.js
+++ b/lib/customUtils.js
@@ -7,6 +7,8 @@ const crypto = require('crypto')
  * that's not an issue here
  * The probability of a collision is extremely small (need 3*10^12 documents to have one chance in a million of a collision)
  * See http://en.wikipedia.org/wiki/Birthday_problem
+ * @param {number} len
+ * @return {string}
  */
 const uid = len => crypto.randomBytes(Math.ceil(Math.max(8, len * 2)))
   .toString('base64')
diff --git a/lib/executor.js b/lib/executor.js
index 61275be..872553f 100755
--- a/lib/executor.js
+++ b/lib/executor.js
@@ -1,3 +1,9 @@
+/**
+ * @callback AsyncFunction
+ * @param {...[*]} args
+ * @return {Promise<*>}
+ */
+
 /**
  * Responsible for sequentially executing actions on the database
  * @private
@@ -9,7 +15,7 @@ class Waterfall {
      *
      * It will change any time `this.waterfall` is called, this is why there is a getter `this.guardian` which retrieves
      * the latest version of the guardian.
-     * @type {Promise<void>}
+     * @type {Promise}
      * @private
      */
     this._guardian = Promise.resolve()
@@ -19,26 +25,20 @@ class Waterfall {
    * Returns a Promise which resolves when all tasks up to when this function is called are done.
    *
    * This Promise cannot reject.
-   * @return {Promise<void>}
+   * @return {Promise}
    */
   get guardian () {
     return this._guardian
   }
 
-  /**
-   * @callback Waterfall~function
-   * @param {...[*]} args
-   * @return {Promise<*>}
-   */
-
   /**
    *
-   * @param {Waterfall~function} func
-   * @return {Waterfall~function}
+   * @param {AsyncFunction} func
+   * @return {AsyncFunction}
    */
   waterfall (func) {
     return (...args) => {
-      this._guardian = this.guardian.then(() => {
+      this._guardian = this.guardian.then(async () => {
         return func(...args)
           .then(result => ({ error: false, result }), result => ({ error: true, result }))
       })
@@ -49,6 +49,11 @@ class Waterfall {
     }
   }
 
+  /**
+   * Shorthand for chaining a promise to the Waterfall
+   * @param promise
+   * @return {Promise}
+   */
   chain (promise) {
     return this.waterfall(() => promise)()
   }
@@ -68,11 +73,11 @@ class Executor {
    * If executor is ready, queue task (and process it immediately if executor was idle)
    * If not, buffer task for later processing
    * @param {Object} task
-   *                 task.this - Object to use as this
-   *                 task.fn - Function to execute
-   *                 task.arguments - Array of arguments, IMPORTANT: only the last argument may be a function (the callback)
-   *                                                                 and the last argument cannot be false/undefined/null
-   * @param {Boolean} forceQueuing Optional (defaults to false) force executor to queue task even if it is not ready
+   * @param {Object} task.this - Object to use as this
+   * @param {function} task.fn - Function to execute
+   * @param {Array} task.arguments - Array of arguments, IMPORTANT: only the last argument may be a function
+   * (the callback) and the last argument cannot be false/undefined/null
+   * @param {Boolean} [forceQueuing = false] Optional (defaults to false) force executor to queue task even if it is not ready
    */
   push (task, forceQueuing) {
     const func = async () => {
@@ -102,7 +107,15 @@ class Executor {
     this.pushAsync(func, forceQueuing)
   }
 
-  pushAsync (task, forceQueuing) {
+  /**
+   * If executor is ready, queue task (and process it immediately if executor was idle)
+   * If not, buffer task for later processing
+   * @param {AsyncFunction} task
+   * @param {boolean} [forceQueuing = false]
+   * @return {Promise<*>}
+   * @async
+   */
+  pushAsync (task, forceQueuing = false) {
     if (this.ready || forceQueuing) return this.queue.waterfall(task)()
     else return this.buffer.waterfall(task)()
   }
diff --git a/lib/persistence.js b/lib/persistence.js
index ac22eb4..93731c6 100755
--- a/lib/persistence.js
+++ b/lib/persistence.js
@@ -61,16 +61,29 @@ class Persistence {
     }
   }
 
+  /**
+   * @callback Persistence~persistCachedDatabaseCallback
+   * @param {Error?} err
+   */
+
   /**
    * Persist cached database
    * This serves as a compaction function since the cache always contains only the number of documents in the collection
    * while the data file is append-only so it may grow larger
-   * @param {Function} callback Optional callback, signature: err
+   * This is an internal function, use compactDataFile which uses the executor
+   * @param {Persistence~persistCachedDatabaseCallback} callback Optional callback, signature: err
    */
   persistCachedDatabase (callback = () => {}) {
     return callbackify(this.persistCachedDatabaseAsync.bind(this))(callback)
   }
 
+  /**
+   * Persist cached database
+   * This serves as a compaction function since the cache always contains only the number of documents in the collection
+   * while the data file is append-only so it may grow larger
+   * This is an internal function, use compactDataFileAsync which uses the executor
+   * @return {Promise<void>}
+   */
   async persistCachedDatabaseAsync () {
     const lines = []
 
@@ -95,13 +108,23 @@ class Persistence {
     this.db.emit('compaction.done')
   }
 
+  /**
+   * @callback Persistence~compactDataFileCallback
+   * @param {Error?} err
+   */
+
   /**
    * Queue a rewrite of the datafile
+   * @param {Persistence~compactDataFileCallback} [callback = () => {}] Optional callback, signature: err
    */
-  compactDatafile () {
-    this.db.executor.push({ this: this, fn: this.persistCachedDatabase, arguments: [] })
+  compactDatafile (callback = () => {}) {
+    this.db.executor.push({ this: this, fn: this.persistCachedDatabase, arguments: [callback] })
   }
 
+  /**
+   * Queue a rewrite of the datafile
+   * @async
+   */
   compactDatafileAsync () {
     return this.db.executor.pushAsync(() => this.persistCachedDatabaseAsync())
   }
@@ -128,16 +151,27 @@ class Persistence {
     if (this.autocompactionIntervalId) clearInterval(this.autocompactionIntervalId)
   }
 
+  /**
+   * @callback Persistence~persistNewStateCallback
+   * @param {Error?} err
+   */
+
   /**
    * Persist new state for the given newDocs (can be insertion, update or removal)
    * Use an append-only format
-   * @param {Array} newDocs Can be empty if no doc was updated/removed
-   * @param {Function} callback Optional, signature: err
+   * @param {string[]} newDocs Can be empty if no doc was updated/removed
+   * @param {Persistence~persistNewStateCallback} [callback = () => {}] Optional, signature: err
    */
   persistNewState (newDocs, callback = () => {}) {
     callbackify(this.persistNewStateAsync.bind(this))(newDocs, err => callback(err))
   }
 
+  /**
+   * Persist new state for the given newDocs (can be insertion, update or removal)
+   * Use an append-only format
+   * @param {string[]} newDocs Can be empty if no doc was updated/removed
+   * @return {Promise}
+   */
   async persistNewStateAsync (newDocs) {
     let toPersist = ''
 
@@ -154,8 +188,16 @@ class Persistence {
   }
 
   /**
-   * From a database's raw data, return the corresponding
-   * machine understandable collection
+   * @typedef rawIndex
+   * @property {string} fieldName
+   * @property {boolean} [unique]
+   * @property {boolean} [sparse]
+   */
+
+  /**
+   * From a database's raw data, return the corresponding machine understandable collection
+   * @param {string} rawData database file
+   * @return {{data: document[], indexes: Object.<string, rawIndex>}}
    */
   treatRawData (rawData) {
     const data = rawData.split('\n')
@@ -190,8 +232,15 @@ class Persistence {
   }
 
   /**
-   * From a database's raw stream, return the corresponding
-   * machine understandable collection
+   * @callback Persistence~treatRawStreamCallback
+   * @param {Error?} err
+   * @param {{data: document[], indexes: Object.<string, rawIndex>}} data
+   */
+
+  /**
+   * From a database's raw data stream, return the corresponding machine understandable collection
+   * @param {Readable} rawStream
+   * @param {Persistence~treatRawStreamCallback} cb
    */
   treatRawStream (rawStream, cb) {
     const dataById = {}
@@ -236,10 +285,21 @@ class Persistence {
     })
   }
 
-  async treatRawStreamAsync (rawStream) {
+  /**
+   * From a database's raw data stream, return the corresponding machine understandable collection
+   * @param {Readable} rawStream
+   * @return {Promise<{data: document[], indexes: Object.<string, rawIndex>}>}
+   * @async
+   */
+  treatRawStreamAsync (rawStream) {
     return promisify(this.treatRawStream.bind(this))(rawStream)
   }
 
+  /**
+   * @callback Persistence~loadDatabaseCallback
+   * @param {Error?} err
+   */
+
   /**
    * Load the database
    * 1) Create all indexes
@@ -248,12 +308,22 @@ class Persistence {
    * This means pulling data out of the data file or creating it if it doesn't exist
    * Also, all data is persisted right away, which has the effect of compacting the database file
    * This operation is very quick at startup for a big collection (60ms for ~10k docs)
-   * @param {Function} callback Optional callback, signature: err
+   * @param {Persistence~loadDatabaseCallback} callback Optional callback, signature: err
    */
   loadDatabase (callback = () => {}) {
     callbackify(this.loadDatabaseAsync.bind(this))(err => callback(err))
   }
 
+  /**
+   * Load the database
+   * 1) Create all indexes
+   * 2) Insert all data
+   * 3) Compact the database
+   * This means pulling data out of the data file or creating it if it doesn't exist
+   * Also, all data is persisted right away, which has the effect of compacting the database file
+   * This operation is very quick at startup for a big collection (60ms for ~10k docs)
+   * @return {Promise<void>}
+   */
   async loadDatabaseAsync () {
     this.db.resetIndexes()
 
@@ -289,14 +359,25 @@ class Persistence {
     this.db.executor.processBuffer()
   }
 
+  /**
+   * @callback Persistence~ensureDirectoryExistsCallback
+   * @param {Error?} err
+   */
+
   /**
    * Check if a directory stat and create it on the fly if it is not the case
-   * cb is optional, signature: err
+   * @param {string} dir
+   * @param {Persistence~ensureDirectoryExistsCallback} [callback = () => {}] optional callback, signature: err
    */
   static ensureDirectoryExists (dir, callback = () => {}) {
     storage.mkdir(dir, { recursive: true }, err => { callback(err) })
   }
 
+  /**
+   * Check if a directory stat and create it on the fly if it is not the case
+   * @param {string} dir
+   * @return {Promise<void>}
+   */
   static async ensureDirectoryExistsAsync (dir) {
     await storage.mkdirAsync(dir, { recursive: true })
   }
@@ -304,6 +385,10 @@ class Persistence {
   /**
    * Return the path the datafile if the given filename is relative to the directory where Node Webkit stores
    * data for this application. Probably the best place to store data
+   * @param {string} appName
+   * @param {string} relativeFilename
+   * @return {string}
+   * @deprecated
    */
   static getNWAppFilename (appName, relativeFilename) {
     return deprecate(() => {
diff --git a/lib/utils.js b/lib/utils.js
index d3d1735..2f86f70 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -1,15 +1,41 @@
-const uniq = (array, iterator) => {
-  if (iterator) return [...(new Map(array.map(x => [iterator(x), x]))).values()]
+/**
+ * Produces a duplicate-free version of the array, using === to test object equality. In particular only the first
+ * occurrence of each value is kept. If you want to compute unique items based on a transformation, pass an iteratee
+ * function.
+ * Heavily inspired by https://underscorejs.org/#uniq
+ * @param {Array} array
+ * @param {function} [iteratee] transformation applied to every element before checking for duplicates. This will not
+ * transform the items in the result.
+ * @return {Array}
+ */
+const uniq = (array, iteratee) => {
+  if (iteratee) return [...(new Map(array.map(x => [iteratee(x), x]))).values()]
   else return [...new Set(array)]
 }
-
-const objectToString = o => Object.prototype.toString.call(o)
-
+/**
+ * Returns true if arg is an Object. Note that JavaScript arrays and functions are objects, while (normal) strings
+ * and numbers are not.
+ * Heavily inspired by https://underscorejs.org/#isObject
+ * @param {*} arg
+ * @return {boolean}
+ */
 const isObject = arg => typeof arg === 'object' && arg !== null
 
-const isDate = d => isObject(d) && objectToString(d) === '[object Date]'
+/**
+ * Returns true if d is a Date.
+ * Heavily inspired by https://underscorejs.org/#isDate
+ * @param {*} d
+ * @return {boolean}
+ */
+const isDate = d => isObject(d) && Object.prototype.toString.call(d) === '[object Date]'
 
-const isRegExp = re => isObject(re) && objectToString(re) === '[object RegExp]'
+/**
+ * Returns true if re is a RegExp.
+ * Heavily inspired by https://underscorejs.org/#isRegExp
+ * @param {*} re
+ * @return {boolean}
+ */
+const isRegExp = re => isObject(re) && Object.prototype.toString.call(re) === '[object RegExp]'
 
 module.exports.uniq = uniq
 module.exports.isDate = isDate