Squashed commit of the following:

commit 47d8422
Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
Date:   Thu Mar 1 13:28:14 2018 +0300

    remove implementation

commit 15fd976
Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
Date:   Thu Mar 1 13:24:23 2018 +0300

    remove implementation

commit 6e4fb76
Merge: 92027d0 ec2395e
Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
Date:   Thu Mar 1 11:14:51 2018 +0300

    Merge remote-tracking branch 'refs/remotes/origin/new-tasks' into new-tasks

commit ec2395e
Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
Date:   Wed Feb 28 13:01:15 2018 +0300

    Squashed commit of the following:

    commit 6215f2c
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Tue Feb 27 17:09:36 2018 +0300

        reverse polish notation task

    commit 64c6b54
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Tue Feb 27 14:32:59 2018 +0300

        title case string task

    commit beb7f37
    Merge: e1ff559 d1a634b
    Author: Aliaksei Bychyk <aleksej.byczyk@tut.by>
    Date:   Tue Feb 27 12:10:53 2018 +0300

        Merge branch 'master' into new-tasks

    commit e1ff559
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Tue Feb 27 11:41:26 2018 +0300

        sync with master and resolve conflicts

    commit 5ecd4da
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Wed Feb 21 15:09:54 2018 +0300

        more tasks with string, arrays, set

    commit a68a740
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Tue Feb 20 18:51:11 2018 +0300

        dependencies optimization

    commit 1d1787e
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Tue Feb 20 13:55:21 2018 +0300

        improve precommit linting and func-names

    commit 8dc6922
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Mon Feb 19 13:17:24 2018 +0300

        remove eslint-plugin-import

    commit 80a74cc
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Mon Feb 19 12:58:47 2018 +0300

        remove eslint-plugin-mocha

    commit bd6d45f
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Fri Feb 16 17:50:31 2018 +0300

        switch repo url type into git+ssh

    commit 93f69c8
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Fri Feb 16 17:32:36 2018 +0300

        remove babel presets and polyfill

    commit 8cd651c
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Fri Feb 16 15:16:26 2018 +0300

        remove upper empty lines

    commit fc1b773
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Fri Feb 16 15:04:01 2018 +0300

        stage-2 and eslint:recommended

    commit 15b20dd
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Fri Feb 16 14:37:49 2018 +0300

        es6 deeper refactoring

    commit a0bad13
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Thu Feb 15 19:02:22 2018 +0300

        arrow parens as needed

    commit 60efb57
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Thu Feb 15 18:51:15 2018 +0300

        string task arrow functions

    commit 5132d49
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Thu Feb 15 17:21:40 2018 +0300

        es6 linting refactoring

    commit 823ee1a
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Thu Feb 15 15:50:22 2018 +0300

        some improvements

    commit 788ebe6
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Thu Feb 15 15:25:35 2018 +0300

        babel-polyfill added

    commit 9f2a7e0
    Author: Aliaksei Bychyk <Aliaksei_Bychyk@epam.com>
    Date:   Thu Feb 15 14:05:17 2018 +0300

        set up es6 syntax capabilities and linting

Author: Aliaksei Bychyk

.eslintrc

@@ -1,4 +1,4 @@
-{ 
+{
   "parserOptions": {
     "sourceType": "module"
   },
@@ -38,4 +38,4 @@
     ],
     "require-yield": 1
   }
-}
+}

task/04-arrays-tasks.js

@@ -44,7 +44,7 @@ export function generateOdds(len) {
 
 
 /**
- * Returns the doubled array - elements of the specified array are repeated twice 
+ * Returns the doubled array - elements of the specified array are repeated twice
  * using original order
  *
  * @param {array} arr
@@ -118,7 +118,7 @@ export function removeFalsyValues(arr) {
  * @return {array}
  *
  * @example
- *    [ 'permanent-internship', 'glutinous-shriek', 'multiplicative-elevation' ] => 
+ *    [ 'permanent-internship', 'glutinous-shriek', 'multiplicative-elevation' ] =>
  *        [ 'PERMANENT-INTERNSHIP', 'GLUTINOUS-SHRIEK', 'MULTIPLICATIVE-ELEVATION' ]
  *    [ 'a', 'b', 'c', 'd', 'e', 'f', 'g' ]  => [ 'A', 'B', 'C', 'D', 'E', 'F', 'G' ]
  */
@@ -415,7 +415,7 @@ export function toStringList(arr) {
 
 
 /**
- * Sorts the specified array by country name first and city name (if countries are 
+ * Sorts the specified array by country name first and city name (if countries are
  * equal) in ascending order.
  *
  * @param {array} arr
@@ -538,11 +538,11 @@ export function group(array, keySelector, valueSelector) {
 
 
 /**
- * Projects each element of the specified array to a sequence and flattens the 
+ * Projects each element of the specified array to a sequence and flattens the
  * resulting sequences into one array.
  *
  * @param {array} arr
- * @param {Function} childrenSelector, a transform const to apply to each element 
+ * @param {Function} childrenSelector, a transform const to apply to each element
  *  that returns an array of children
  * @return {array}
  *

task/08-objects-tasks.js

@@ -63,7 +63,7 @@ export function fromJSON(proto, json) {
 /**
  * Css selectors builder
  *
- * Each complex selector can consists of type, id, class, attribute, pseudo-class and 
+ * Each complex selector can consists of type, id, class, attribute, pseudo-class and
  * pseudo-element selectors:
  *
  *    element#id.class[attr]:pseudoClass::pseudoElement
@@ -72,10 +72,10 @@ export function fromJSON(proto, json) {
  *
  * All types of selectors can be combined using the combinators ' ','+','~','>' .
  *
- * The task is to design a single class, independent classes or classes hierarchy and 
+ * The task is to design a single class, independent classes or classes hierarchy and
  * implement the functionality
  * to build the css selectors using the provided cssSelectorBuilder.
- * Each selector should have the stringify() method to output the string repsentation 
+ * Each selector should have the stringify() method to output the string repsentation
  * according to css specification.
  *
  * Provided cssSelectorBuilder should be used as facade only to create your own classes,
@@ -84,17 +84,17 @@ export function fromJSON(proto, json) {
  *       return new MySuperBaseElementSelector(...)...
  *   },
  *
- * The design of class(es) is totally up to you, but try to make it as simple, clear 
+ * The design of class(es) is totally up to you, but try to make it as simple, clear
  * and readable as possible.
  *
  * @example
  *
  *  var builder = cssSelectorBuilder;
  *
- *  builder.id('main').class('container').class('editable').stringify() => 
+ *  builder.id('main').class('container').class('editable').stringify() =>
  *    '#main.container.editable'
  *
- *  builder.element('a').attr('href$=".png"').pseudoClass('focus').stringify() => 
+ *  builder.element('a').attr('href$=".png"').pseudoClass('focus').stringify() =>
  *    'a[href$=".png"]:focus'
  *
  *  builder.combine(

task/11-katas-2-tasks.js

@@ -2,9 +2,9 @@
 /**
  * Returns the bank account number parsed from specified string.
  *
- * You work for a bank, which has recently purchased an ingenious machine to assist 
+ * You work for a bank, which has recently purchased an ingenious machine to assist
  * in reading letters and faxes sent in by branch offices.
- * The machine scans the paper documents, and produces a string with a bank account 
+ * The machine scans the paper documents, and produces a string with a bank account
  * that looks like this:
  *
  *    _  _     _  _  _  _  _
@@ -14,7 +14,7 @@
  * Each string contains an account number written using pipes and underscores.
  * Each account number should have 9 digits, all of which should be in the range 0-9.
  *
- * Your task is to write a function that can take bank account string and parse it 
+ * Your task is to write a function that can take bank account string and parse it
  * into actual account numbers.
  *
  * @param {string} bankAccount
@@ -42,7 +42,7 @@ export function parseBankAccount(bankAccount) {
 
 
 /**
- * Returns the string, but with line breaks inserted at just the right places to make 
+ * Returns the string, but with line breaks inserted at just the right places to make
  * sure that no line is longer than the specified column number.
  * Lines can be broken at word boundaries only.
  *
@@ -114,7 +114,7 @@ export function getPokerHandRank(hand) {
 
 /**
  * Returns the rectangles sequence of specified figure.
- * The figure is ASCII multiline string comprised of minus signs -, plus signs +, 
+ * The figure is ASCII multiline string comprised of minus signs -, plus signs +,
  * vertical bars | and whitespaces.
  * The task is to break the figure in the rectangles it is made of.
  *

task/12-katas-3-tasks.js

@@ -1,7 +1,7 @@
 
 /**
  * Returns true if word occurrs in the specified word snaking puzzle.
- * Each words can be constructed using "snake" path inside a grid with top, left, 
+ * Each words can be constructed using "snake" path inside a grid with top, left,
  * right and bottom directions.
  * Each char can be used only once ("snake" should not cross itself).
  *
@@ -39,7 +39,7 @@ export function findStringInSnakingPuzzle(puzzle, searchStr) {
  * The order of permutations does not matter.
  *
  * @param {string} chars
- * @return {Iterable.<string>} all posible strings constructed with the chars from 
+ * @return {Iterable.<string>} all posible strings constructed with the chars from
  *    the specfied string
  *
  * @example
@@ -56,9 +56,9 @@ export function* getPermutations(chars) {
  * Returns the most profit from stock quotes.
  * Stock quotes are stores in an array in order of date.
  * The stock profit is the difference in prices in buying and selling stock.
- * Each day, you can either buy one unit of stock, sell any number of stock units 
+ * Each day, you can either buy one unit of stock, sell any number of stock units
  * you have already bought, or do nothing.
- * Therefore, the most profit is the maximum difference of all pairs in a sequence 
+ * Therefore, the most profit is the maximum difference of all pairs in a sequence
  * of stock prices.
  *
  * @param {array} quotes

task/13-more-tasks.js

@@ -0,0 +1,80 @@
+/**
+ * Takes two strings including only letters from a to z.
+ * Returns a new sorted string containing distinct letters.
+ *
+ * @param {string} value1
+ * @param {string} value2
+ * @return {string}
+ *
+ * @example
+ *   'azy', 'bk' => 'abkyz'
+ *   'zxxlal','laxk'    => 'aklxz'
+ *   'abcdefghijklmnop',  'lmnopqrstuvwxyz'  => 'abcdefghijklmnopqrstuvwxyz'
+ */
+export function distinctLettersString(value1, value2) {
+  /* implement your code here */
+  throw new Error('Not implemented');
+}
+
+
+/**
+ * Takes a string with any characters.
+ * Returns an object containing appearence of every distinct letters in lower case.
+ *
+ * @param {string} value
+ * @return {Object}
+ *
+ * @example
+ *  'Who you are, Buddy?' => { a:1, d:2, e:1, h:1, o:2, r:1, u:2, y:2 }
+ *
+ */
+
+export function lowerLetters(value) {
+  /* implement your code here */
+  throw new Error('Not implemented');
+}
+
+/**
+ * Write a function that will convert a string into title case, given an optional
+ * list of exception (minor words). The list of minor words will be given as a
+ * string with each word separated by a space. Your function should ignore the
+ * case of the minor words string - it should behave in the same way even if the
+ * case of the minor word is changed
+ *
+ * @param {string} the original string to be converted
+ * @param {string} list of minor words that must always be lowercase except for
+ *                  the first word in the string
+ * @return {string}
+ *
+ * @example
+ *    'a clash if KINGS', 'a an the of'  =>  'A Clash of Kings'
+ *    'THE WIND IN THE WILLOWS', 'The In'  => 'The Wind in the Willows'
+ *    'the quick brown fox'  => 'The Quick Brown Fox'
+ */
+
+export function titleCaseConvert(title, minorWords) {
+  /* implement your code here */
+  throw new Error('Not implemented');
+}
+
+/**
+ * Your job is to create a calculator which evaluates expressions in Reverse Polish
+ * notation (https://en.wikipedia.org/wiki/Reverse_Polish_notation). Empty expression
+ * should evaluate to 0. Expression without operation returns the last number.
+ *
+ * @param {string} RPN string, each number and operation separated by a space
+ *
+ * @return {Number}
+ *
+ * @example
+ *  ''  =>  0  // empty expression returns 0
+ *  '1 2 3'  =>  3  // expression without operation returns the last number
+ *  '4 2 +'  =>  6  // 4 + 2
+ *  '2 5 * 2 + 3 /'  =>  4   //  ((5 * 2) + 2) / 3
+ *  '5 1 2 + 4 * + 3 -'  =>  14   // 5 + ((1 + 2) * 4) -3
+ */
+
+export function calcRPN(expr) {
+  /* implement your code here */
+  throw new Error('Not implemented');
+}

test/13-more-tasks.js

@@ -0,0 +1,33 @@
+import assert from 'assert';
+
+import { distinctLettersString, lowerLetters, titleCaseConvert, calcRPN } from '../task/13-more-tasks';
+
+it.optional = require('../extensions/it-optional');
+
+describe('13-more-tasks', () => {
+  it.optional('distinctLettersString should return a new sorted string with distinct letters', () => {
+    assert.equal('abcdefklmopqwxy',
+      distinctLettersString('xyaabbbccccdefww', 'xxxxyyyyabklmopq'));
+    assert.equal('abcdefghilnoprstu',
+      distinctLettersString('loopingisfunbutdangerous', 'lessdangerousthancoding'));
+  });
+
+  it.optional('lowerLetters should return an object of every distinct letters', () => {
+    assert.deepEqual({ e: 2, n: 2, r: 1, t: 2 }, lowerLetters('Internet 42'));
+    assert.deepEqual({ a: 3, d: 1, f: 2, p: 1, x: 1 }, lowerLetters('$0 af0HOE@ /xfda2 24pa'));
+  });
+
+  it.optional('titleCaseConvert should return converted into title case string', () => {
+    assert.equal('A Clash of Kings', titleCaseConvert('a clash of KINGS', 'a an the of'));
+    assert.equal('The Wind in the Willows', titleCaseConvert('THE WIND IN THE WILLOWS', 'The In'));
+    assert.equal('The Quick Brown Fox', titleCaseConvert('the quick brown fox'));
+  });
+
+  it.optional('calcRPN should calculate Reverse Polish notation expression', () => {
+    assert.equal(0, calcRPN(''));
+    assert.equal(3, calcRPN('1 2 3'));
+    assert.equal(6, calcRPN('4 2 +'));
+    assert.equal(4, calcRPN('2 5 * 2 + 3 /'));
+    assert.equal(14, calcRPN('5 1 2 + 4 * + 3 -'));
+  });
+});