From dcedc10fa0cec134d10ae44079e85297046e209d Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Sat, 9 Dec 2017 17:24:34 +0200
Subject: [PATCH 1/6] Difference between arrays

---
 README.md                             | 10 ++++++++++
 snippets/difference-between-arrays.md |  8 ++++++++
 2 files changed, 18 insertions(+)
 create mode 100644 snippets/difference-between-arrays.md

diff --git a/README.md b/README.md
index 782f34c86..00b205444 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,7 @@
 * [Capitalize first letter](#capitalize-first-letter)
 * [Count occurences of a value in array](#count-occurences-of-a-value-in-array)
 * [Current URL](#current-url)
+* [Difference between arrays](#difference-between-arrays)
 * [Distance between two points](#distance-between-two-points)
 * [Even or odd number](#even-or-odd-number)
 * [Factorial](#factorial)
@@ -86,6 +87,15 @@ Use `window.location.href` to get current URL.
 var currentUrl = _ => window.location.href;
 ```
 
+### Difference between arrays
+
+Use `filter()` to remove values that are not part of `values`, determined using `indexOf()`.
+
+```js
+var difference = (arr, values) =>
+  arr.filter(v => values.indexOf(v) === -1);
+```
+
 ### Distance between two points
 
 Use `Math.pow()` and `Math.sqrt()` to calculate the Euclidean distance between two points.
diff --git a/snippets/difference-between-arrays.md b/snippets/difference-between-arrays.md
new file mode 100644
index 000000000..5db03e029
--- /dev/null
+++ b/snippets/difference-between-arrays.md
@@ -0,0 +1,8 @@
+### Difference between arrays
+
+Use `filter()` to remove values that are not part of `values`, determined using `indexOf()`.
+
+```js
+var difference = (arr, values) =>
+  arr.filter(v => values.indexOf(v) === -1);
+```

From 9c9e2114f6d672ea88999cb04db4e740d700ba58 Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Sun, 10 Dec 2017 15:02:07 +0200
Subject: [PATCH 2/6] Similarity between arrays, object from key-value pairs

---
 README.md                               | 22 +++++++++++++++++++++-
 snippets/difference-between-arrays.md   |  2 +-
 snippets/object-from-key-value-pairs.md |  8 ++++++++
 snippets/similarity-between-arrays.md   |  8 ++++++++
 4 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 snippets/object-from-key-value-pairs.md
 create mode 100644 snippets/similarity-between-arrays.md

diff --git a/README.md b/README.md
index 00b205444..daf8d81dd 100644
--- a/README.md
+++ b/README.md
@@ -23,12 +23,14 @@
 * [Initialize array with range](#initialize-array-with-range)
 * [Initialize array with values](#initialize-array-with-values)
 * [Measure time taken by function](#measure-time-taken-by-function)
+* [Object from key value pairs](#object-from-key-value-pairs)
 * [Powerset](#powerset)
 * [Random number in range](#random-number-in-range)
 * [Randomize order of array](#randomize-order-of-array)
 * [Redirect to url](#redirect-to-url)
 * [RGB to hexadecimal](#rgb-to-hexadecimal)
 * [Scroll to top](#scroll-to-top)
+* [Similarity between arrays](#similarity-between-arrays)
 * [Sort characters in string (alphabetical)](#sort-characters-in-string-alphabetical)
 * [Sum of array of numbers](#sum-of-array-of-numbers)
 * [Swap values of two variables](#swap-values-of-two-variables)
@@ -89,7 +91,7 @@ var currentUrl = _ => window.location.href;
 
 ### Difference between arrays
 
-Use `filter()` to remove values that are not part of `values`, determined using `indexOf()`.
+Use `filter()` to remove values that are part of `values`, determined using `indexOf()`.
 
 ```js
 var difference = (arr, values) =>
@@ -190,6 +192,15 @@ var timeTaken = (f,...args) => {
 }
 ```
 
+### Object from key-value pairs
+
+Use `map()` to create objects for each key-value pair, combine with `Object.assign()`.
+
+```js
+var objectFromPairs = arr =>
+  Object.assign(...arr.map( v => {return {[v[0]] : v[1]};} ));
+```
+
 ### Powerset
 
 Use `reduce()` combined with `map()` to iterate over elements and combine into an array containing all combinations. 
@@ -250,6 +261,15 @@ var scrollToTop = _ => {
 }
 ```
 
+### Similarity between arrays
+
+Use `filter()` to remove values that are not part of `values`, determined using `indexOf()`.
+
+```js
+var difference = (arr, values) =>
+  arr.filter(v => values.indexOf(v) !== -1);
+```
+
 ### Sort characters in string (alphabetical)
 
 Split the string using `split('')`, `sort()` utilizing `localeCompare()`, recombine using `join('')`.
diff --git a/snippets/difference-between-arrays.md b/snippets/difference-between-arrays.md
index 5db03e029..01e6c5883 100644
--- a/snippets/difference-between-arrays.md
+++ b/snippets/difference-between-arrays.md
@@ -1,6 +1,6 @@
 ### Difference between arrays
 
-Use `filter()` to remove values that are not part of `values`, determined using `indexOf()`.
+Use `filter()` to remove values that are part of `values`, determined using `indexOf()`.
 
 ```js
 var difference = (arr, values) =>
diff --git a/snippets/object-from-key-value-pairs.md b/snippets/object-from-key-value-pairs.md
new file mode 100644
index 000000000..e241fcdc9
--- /dev/null
+++ b/snippets/object-from-key-value-pairs.md
@@ -0,0 +1,8 @@
+### Object from key-value pairs
+
+Use `map()` to create objects for each key-value pair, combine with `Object.assign()`.
+
+```js
+var objectFromPairs = arr =>
+  Object.assign(...arr.map( v => {return {[v[0]] : v[1]};} ));
+```
diff --git a/snippets/similarity-between-arrays.md b/snippets/similarity-between-arrays.md
new file mode 100644
index 000000000..b4d08de0a
--- /dev/null
+++ b/snippets/similarity-between-arrays.md
@@ -0,0 +1,8 @@
+### Similarity between arrays
+
+Use `filter()` to remove values that are not part of `values`, determined using `indexOf()`.
+
+```js
+var difference = (arr, values) =>
+  arr.filter(v => values.indexOf(v) !== -1);
+```

From 542a08cf2ad78b29b0049cd789f3c6da12dadc7e Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Sun, 10 Dec 2017 15:21:35 +0200
Subject: [PATCH 3/6] Generic currying

---
 README.md         | 13 +++++++++++++
 snippets/curry.md | 11 +++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 snippets/curry.md

diff --git a/README.md b/README.md
index daf8d81dd..0a64be235 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,7 @@
 * [Capitalize first letter](#capitalize-first-letter)
 * [Count occurences of a value in array](#count-occurences-of-a-value-in-array)
 * [Current URL](#current-url)
+* [Curry](#curry)
 * [Difference between arrays](#difference-between-arrays)
 * [Distance between two points](#distance-between-two-points)
 * [Even or odd number](#even-or-odd-number)
@@ -89,6 +90,18 @@ Use `window.location.href` to get current URL.
 var currentUrl = _ => window.location.href;
 ```
 
+### Curry
+
+Use recursion.
+If the number of provided arguments (`args`) is sufficient, call the passed function `f`.
+Otherwise return a curried function `f` that expects the rest of the arguments.
+
+```js
+curry = f =>
+  (...args) =>
+    args.length >= f.length ? f(...args) : (...otherArgs) => curry(f)(...args, ...otherArgs)
+```
+
 ### Difference between arrays
 
 Use `filter()` to remove values that are part of `values`, determined using `indexOf()`.
diff --git a/snippets/curry.md b/snippets/curry.md
new file mode 100644
index 000000000..9a090fe53
--- /dev/null
+++ b/snippets/curry.md
@@ -0,0 +1,11 @@
+### Curry
+
+Use recursion.
+If the number of provided arguments (`args`) is sufficient, call the passed function `f`.
+Otherwise return a curried function `f` that expects the rest of the arguments.
+
+```js
+curry = f =>
+  (...args) =>
+    args.length >= f.length ? f(...args) : (...otherArgs) => curry(f)(...args, ...otherArgs)
+```

From 2fa6e7bba8a2b1a3972ed80f165966d2962efd49 Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Sun, 10 Dec 2017 16:55:32 +0200
Subject: [PATCH 4/6] Escape regexp

---
 README.md                             | 11 +++++++++++
 snippets/escape-regular-expression.md |  9 +++++++++
 2 files changed, 20 insertions(+)
 create mode 100644 snippets/escape-regular-expression.md

diff --git a/README.md b/README.md
index 0a64be235..12b807a8e 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,7 @@
 * [Curry](#curry)
 * [Difference between arrays](#difference-between-arrays)
 * [Distance between two points](#distance-between-two-points)
+* [Escape regular expression](#escape-regular-expression)
 * [Even or odd number](#even-or-odd-number)
 * [Factorial](#factorial)
 * [Fibonacci array generator](#fibonacci-array-generator)
@@ -120,6 +121,16 @@ var distance = x0, y0, x1, y1 =>
   Math.sqrt(Math.pow(x1-x0, 2) + Math.pow(y1 - y0, 2))
 ```
 
+### Escape regular expression
+
+Use `replace()` to escape special characters.
+
+```js
+escapeRegExp = s =>
+  s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+}
+```
+
 ### Even or odd number
 
 Use `Math.abs()` to extend logic to negative numbers, check using the modulo (`%`) operator.
diff --git a/snippets/escape-regular-expression.md b/snippets/escape-regular-expression.md
new file mode 100644
index 000000000..b653c066d
--- /dev/null
+++ b/snippets/escape-regular-expression.md
@@ -0,0 +1,9 @@
+### Escape regular expression
+
+Use `replace()` to escape special characters.
+
+```js
+escapeRegExp = s =>
+  s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+}
+```

From b30a7af75683993587e77d48609e792adf7e8435 Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Sun, 10 Dec 2017 17:59:07 +0200
Subject: [PATCH 5/6] Housekeeping, head, tail, init and last of list

---
 README.md                             | 44 +++++++++++++++++++++++++--
 snippets/curry.md                     |  2 +-
 snippets/escape-regular-expression.md |  2 +-
 snippets/head-of-list.md              |  8 +++++
 snippets/initial-of-list.md           |  8 +++++
 snippets/last-of-list.md              |  8 +++++
 snippets/tail-of-list.md              |  8 +++++
 7 files changed, 76 insertions(+), 4 deletions(-)
 create mode 100644 snippets/head-of-list.md
 create mode 100644 snippets/initial-of-list.md
 create mode 100644 snippets/last-of-list.md
 create mode 100644 snippets/tail-of-list.md

diff --git a/README.md b/README.md
index 12b807a8e..14410e196 100644
--- a/README.md
+++ b/README.md
@@ -22,8 +22,11 @@
 * [Fibonacci array generator](#fibonacci-array-generator)
 * [Flatten array](#flatten-array)
 * [Greatest common divisor (GCD)](#greatest-common-divisor-gcd)
+* [Head of list](#head-of-list)
+* [Initial of list](#initial-of-list)
 * [Initialize array with range](#initialize-array-with-range)
 * [Initialize array with values](#initialize-array-with-values)
+* [Last of list](#last-of-list)
 * [Measure time taken by function](#measure-time-taken-by-function)
 * [Object from key value pairs](#object-from-key-value-pairs)
 * [Powerset](#powerset)
@@ -36,6 +39,7 @@
 * [Sort characters in string (alphabetical)](#sort-characters-in-string-alphabetical)
 * [Sum of array of numbers](#sum-of-array-of-numbers)
 * [Swap values of two variables](#swap-values-of-two-variables)
+* [Tail of list](#tail-of-list)
 * [Unique values of array](#unique-values-of-array)
 * [URL parameters](#url-parameters)
 * [UUID generator](#uuid-generator)
@@ -98,7 +102,7 @@ If the number of provided arguments (`args`) is sufficient, call the passed func
 Otherwise return a curried function `f` that expects the rest of the arguments.
 
 ```js
-curry = f =>
+var curry = f =>
   (...args) =>
     args.length >= f.length ? f(...args) : (...otherArgs) => curry(f)(...args, ...otherArgs)
 ```
@@ -126,7 +130,7 @@ var distance = x0, y0, x1, y1 =>
 Use `replace()` to escape special characters.
 
 ```js
-escapeRegExp = s =>
+var escapeRegExp = s =>
   s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
 }
 ```
@@ -183,6 +187,24 @@ Otherwise, return the GCD of `y` and the remainder of the division `x/y`.
 var gcd = (x , y) => !y ? x : gcd(y, x % y);
 ```
 
+### Head of list
+
+Return `arr[0]`.
+
+```js
+var head = arr => arr[0];
+}
+```
+
+### Initial of list
+
+Return `arr.slice(0,-1)`.
+
+```js
+var initial = arr => arr.slice(0,-1);
+}
+```
+
 ### Initialize array with range
 
 Use `Array(end-start)` to create an array of the desired length, `map()` to fill with the desired values in a range.
@@ -203,6 +225,15 @@ var initializeArray = (n, v = 0) =>
   Array(n).fill(v);
 ```
 
+### Last of list
+
+Return `arr.slice(-1)[0]`.
+
+```js
+var initial = arr => arr.slice(-1)[0];
+}
+```
+
 ### Measure time taken by function
 
 Use `performance.now()` to get start and end time for the function, `console.log()` the time taken.
@@ -320,6 +351,15 @@ Use array destructuring to swap values between two variables.
 [varA, varB] = [varB, varA];
 ```
 
+### Tail of list
+
+Return `arr.slice(1)`.
+
+```js
+var tail = arr => arr.slice(1);
+}
+```
+
 ### Unique values of array
 
 Use `reduce()` to accumulate all unique values in an array.
diff --git a/snippets/curry.md b/snippets/curry.md
index 9a090fe53..a30e74433 100644
--- a/snippets/curry.md
+++ b/snippets/curry.md
@@ -5,7 +5,7 @@ If the number of provided arguments (`args`) is sufficient, call the passed func
 Otherwise return a curried function `f` that expects the rest of the arguments.
 
 ```js
-curry = f =>
+var curry = f =>
   (...args) =>
     args.length >= f.length ? f(...args) : (...otherArgs) => curry(f)(...args, ...otherArgs)
 ```
diff --git a/snippets/escape-regular-expression.md b/snippets/escape-regular-expression.md
index b653c066d..00367ec3d 100644
--- a/snippets/escape-regular-expression.md
+++ b/snippets/escape-regular-expression.md
@@ -3,7 +3,7 @@
 Use `replace()` to escape special characters.
 
 ```js
-escapeRegExp = s =>
+var escapeRegExp = s =>
   s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
 }
 ```
diff --git a/snippets/head-of-list.md b/snippets/head-of-list.md
new file mode 100644
index 000000000..0fec83c44
--- /dev/null
+++ b/snippets/head-of-list.md
@@ -0,0 +1,8 @@
+### Head of list
+
+Return `arr[0]`.
+
+```js
+var head = arr => arr[0];
+}
+```
diff --git a/snippets/initial-of-list.md b/snippets/initial-of-list.md
new file mode 100644
index 000000000..a5afb4f04
--- /dev/null
+++ b/snippets/initial-of-list.md
@@ -0,0 +1,8 @@
+### Initial of list
+
+Return `arr.slice(0,-1)`.
+
+```js
+var initial = arr => arr.slice(0,-1);
+}
+```
diff --git a/snippets/last-of-list.md b/snippets/last-of-list.md
new file mode 100644
index 000000000..2bbf2fe12
--- /dev/null
+++ b/snippets/last-of-list.md
@@ -0,0 +1,8 @@
+### Last of list
+
+Return `arr.slice(-1)[0]`.
+
+```js
+var initial = arr => arr.slice(-1)[0];
+}
+```
diff --git a/snippets/tail-of-list.md b/snippets/tail-of-list.md
new file mode 100644
index 000000000..5c52c2ac4
--- /dev/null
+++ b/snippets/tail-of-list.md
@@ -0,0 +1,8 @@
+### Tail of list
+
+Return `arr.slice(1)`.
+
+```js
+var tail = arr => arr.slice(1);
+}
+```

From 4f299f070564145ed6463b3d74a7fcb121732fb8 Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Sun, 10 Dec 2017 18:00:03 +0200
Subject: [PATCH 6/6] Housekeeping

---
 README.md                   | 4 ----
 snippets/head-of-list.md    | 1 -
 snippets/initial-of-list.md | 1 -
 snippets/last-of-list.md    | 1 -
 snippets/tail-of-list.md    | 1 -
 5 files changed, 8 deletions(-)

diff --git a/README.md b/README.md
index 14410e196..c1d9f844e 100644
--- a/README.md
+++ b/README.md
@@ -193,7 +193,6 @@ Return `arr[0]`.
 
 ```js
 var head = arr => arr[0];
-}
 ```
 
 ### Initial of list
@@ -202,7 +201,6 @@ Return `arr.slice(0,-1)`.
 
 ```js
 var initial = arr => arr.slice(0,-1);
-}
 ```
 
 ### Initialize array with range
@@ -231,7 +229,6 @@ Return `arr.slice(-1)[0]`.
 
 ```js
 var initial = arr => arr.slice(-1)[0];
-}
 ```
 
 ### Measure time taken by function
@@ -357,7 +354,6 @@ Return `arr.slice(1)`.
 
 ```js
 var tail = arr => arr.slice(1);
-}
 ```
 
 ### Unique values of array
diff --git a/snippets/head-of-list.md b/snippets/head-of-list.md
index 0fec83c44..b0b8e6305 100644
--- a/snippets/head-of-list.md
+++ b/snippets/head-of-list.md
@@ -4,5 +4,4 @@ Return `arr[0]`.
 
 ```js
 var head = arr => arr[0];
-}
 ```
diff --git a/snippets/initial-of-list.md b/snippets/initial-of-list.md
index a5afb4f04..8ed934543 100644
--- a/snippets/initial-of-list.md
+++ b/snippets/initial-of-list.md
@@ -4,5 +4,4 @@ Return `arr.slice(0,-1)`.
 
 ```js
 var initial = arr => arr.slice(0,-1);
-}
 ```
diff --git a/snippets/last-of-list.md b/snippets/last-of-list.md
index 2bbf2fe12..4397d5980 100644
--- a/snippets/last-of-list.md
+++ b/snippets/last-of-list.md
@@ -4,5 +4,4 @@ Return `arr.slice(-1)[0]`.
 
 ```js
 var initial = arr => arr.slice(-1)[0];
-}
 ```
diff --git a/snippets/tail-of-list.md b/snippets/tail-of-list.md
index 5c52c2ac4..1b5adfd83 100644
--- a/snippets/tail-of-list.md
+++ b/snippets/tail-of-list.md
@@ -4,5 +4,4 @@ Return `arr.slice(1)`.
 
 ```js
 var tail = arr => arr.slice(1);
-}
 ```