diff --git a/README.md b/README.md
index 776d746ef..c15a1a0cb 100644
--- a/README.md
+++ b/README.md
@@ -44,6 +44,7 @@
 * [Similarity between arrays](#similarity-between-arrays)
 * [Sum of array of numbers](#sum-of-array-of-numbers)
 * [Tail of list](#tail-of-list)
+* [Take every nth element](#take-every-nth-element)
 * [Take right](#take-right)
 * [Take](#take)
 * [Unique values of array](#unique-values-of-array)
@@ -61,8 +62,9 @@
 
 ### Function
 * [Chain asynchronous functions](#chain-asynchronous-functions)
+* [Compose functions](#compose-functions)
 * [Curry](#curry)
-* [Pipe](#pipe)
+* [Pipe functions](#pipe-functions)
 * [Promisify](#promisify)
 * [Run promises in series](#run-promises-in-series)
 * [Sleep](#sleep)
@@ -85,9 +87,11 @@
 * [Speech synthesis (experimental)](#speech-synthesis-experimental)
 
 ### Node
-* [Write json to file](#write-json-to-file)
+* [Read file as array of lines](#read-file-as-array-of-lines)
+* [Write JSON to file](#write-json-to-file)
 
 ### Object
+* [Clean JSON object](#clean-json-object)
 * [Object from key value pairs](#object-from-key-value-pairs)
 * [Object to key value pairs](#object-to-key-value-pairs)
 * [Shallow clone object](#shallow-clone-object)
@@ -102,6 +106,7 @@
 * [Truncate a string](#truncate-a-string)
 
 ### Utility
+* [3 digit hexcode to 6 digit hexcode](#3-digit-hexcode-to-6-digit-hexcode)
 * [Escape regular expression](#escape-regular-expression)
 * [Get native type of value](#get-native-type-of-value)
 * [Hexcode to RGB](#hexcode-to-rgb)
@@ -117,7 +122,6 @@
 * [Random integer in range](#random-integer-in-range)
 * [Random number in range](#random-number-in-range)
 * [RGB to hexadecimal](#rgb-to-hexadecimal)
-* [Swap values of two variables](#swap-values-of-two-variables)
 * [URL parameters](#url-parameters)
 * [UUID generator](#uuid-generator)
 * [Validate email](#validate-email)
@@ -128,11 +132,11 @@
 
 ### Array concatenation
 
-Use `Array.concat()` to concatenate an array with any additional arrays and/or values, specified in `args`.
+Use Array spread operators (`...`) to concatenate an array with any additional arrays and/or values, specified in `args`.
 
 ```js
-const ArrayConcat = (arr, ...args) => [].concat(arr, ...args); 
-// ArrayConcat([1], [1, 2, 3, [4]]) -> [1, 2, 3, [4]]
+const ArrayConcat = (arr, ...args) => [...arr,...args]; 
+// ArrayConcat([1], [1, 2, 3, [4]]) -> [1, 1, 2, 3, [4]]
 ```
 
 [⬆ back to top](#table-of-contents)
@@ -213,11 +217,11 @@ const union = (a, b) => Array.from(new Set([...a, ...b]));
 
 ### Array without
 
-Use `Array.filter()` to create an array excluding all given values.
+Use `Array.filter()` to create an array excluding(using `!Array.includes()`) all given values.
 
 ```js
-const without = (arr, ...args) => arr.filter(v => args.indexOf(v) === -1);
-// without[2, 1, 2, 3], 1, 2) -> [3]
+const without = (arr, ...args) => arr.filter(v => !args.includes(v));
+// without([2, 1, 2, 3], 1, 2) -> [3]
 // without([2, 1, 2, 3, 4, 5, 5, 5, 3, 2, 7, 7], 3, 1, 5, 2) -> [ 4, 7, 7 ]
 ```
 
@@ -231,7 +235,7 @@ If lengths of the argument-arrays vary, `undefined` is used where no value could
 
 ```js
 const zip = (...arrays) => {
-  const maxLength = Math.max.apply(null, arrays.map(a => a.length));
+  const maxLength = Math.max(...arrays.map(x => x.length));
   return Array.from({length: maxLength}).map((_, i) => {
    return Array.from({length: arrays.length}, (_, k) => arrays[k][i]);
   })
@@ -434,7 +438,7 @@ You can omit `start` to use a default value of `0`.
 
 ```js
 const initializeArrayRange = (end, start = 0) =>
-  Array.apply(null, Array(end - start)).map((v, i) => i + start);
+  Array.from({ length: end - start }).map((v, i) => i + start);
 // initializeArrayRange(5) -> [0,1,2,3,4]
 ```
 
@@ -551,6 +555,17 @@ const tail = arr => arr.length > 1 ? arr.slice(1) : arr;
 
 [⬆ back to top](#table-of-contents)
 
+### Take every nth element
+
+Use `Array.filter()` to create a new array that contains every nth element of a given array.
+
+```js
+const everynth = (arr, nth) => arr.filter((e, i) => i % nth === 0);
+// everynth([1,2,3,4,5,6], 2) -> [ 1, 3, 5 ]
+```
+
+[⬆ back to top](#table-of-contents)
+
 ### Take right
 
 Use `Array.slice()` to create a slice of the array with `n` elements taken from the end.
@@ -707,6 +722,22 @@ chainAsync([
 
 [⬆ back to top](#table-of-contents)
 
+### Compose functions
+
+Use `Array.reduce()` to perform right-to-left function composition.
+The last (rightmost) function can accept one or more arguments; the remaining functions must be unary.
+
+```js
+const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)));
+/*
+const add5 = x => x + 5
+const multiply = (x, y) => x * y
+const multiplyAndAdd5 = compose(add5, multiply)
+multiplyAndAdd5(5, 2) -> 15
+*/
+```
+[⬆ back to top](#table-of-contents)
+
 ### Curry
 
 Use recursion.
@@ -725,9 +756,9 @@ const curry = (fn, arity = fn.length, ...args) =>
 
 [⬆ back to top](#table-of-contents)
 
-### Pipe
+### Pipe functions
 
-Use `Array.reduce()` to perform left-to-right function composition.
+Use `Array.reduce()` with the spread operator (`...`) to perform left-to-right function composition.
 The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
 
 ```js
@@ -967,7 +998,29 @@ const speak = message => {
 [⬆ back to top](#table-of-contents)
 ## Node
 
-### Write a JSON to a file
+### Read file as array of lines
+
+Use `readFileSync` function in `fs` node package to create a `Buffer` from a file.
+convert buffer to string using `toString(encoding)` function.
+creating an array from contents of file by `split`ing file content line by line(each `\n`).
+
+  ```js
+const fs = require('fs');
+const readFileToArray = filename => fs.readFileSync(filename).toString('UTF8').split('\n');
+/*
+  contents of test.txt :
+    line1
+    line2
+    line3
+    ___________________________
+  let arr = readFileToArray('test.txt')
+  console.log(arr) // -> ['line1', 'line2', 'line3']
+ */
+```
+
+[⬆ back to top](#table-of-contents)
+
+### Write JSON to file
 
 Use `fs.writeFile()`, template literals and `JSON.stringify()` to write a `json` object to a `.json` file.
 
@@ -980,6 +1033,30 @@ const jsonToFile = (obj, filename) => fs.writeFile(`${filename}.json`, JSON.stri
 [⬆ back to top](#table-of-contents)
 ## Object
 
+### Clean JSON object
+
+Use `Object.keys()` method to loop over given json object and deleting keys that are not `include`d in given array.
+also if you give it a special key(`childIndicator`) it will search deeply inside it to apply function to inner objects too.
+
+```js
+const cleanObj = (obj, keysToKeep = [], childIndicator) => {
+  Object.keys(obj).forEach(key => {
+    if (key === childIndicator) {
+      cleanObj(obj[key], keysToKeep, childIndicator);
+    } else if (!keysToKeep.includes(key)) {
+      delete obj[key];
+    }
+  })
+}
+/*
+  testObj = {a: 1, b: 2, children: {a: 1, b: 2}}
+  cleanObj(testObj, ["a"],"children")
+  console.log(testObj)// { a: 1, children : { a: 1}}
+*/
+```
+
+[⬆ back to top](#table-of-contents)
+
 ### Object from key-value pairs
 
 Use `Array.reduce()` to create and combine key-value pairs.
@@ -1114,6 +1191,20 @@ const truncate = (str, num) =>
 [⬆ back to top](#table-of-contents)
 ## Utility
 
+### 3-digit hexcode to 6-digit hexcode
+
+Use `Array.map()`, `split()` and `Array.join()` to join the mapped array for converting a three-digit RGB notated hexadecimal colorcode to the six-digit form.
+
+```js
+const convertHex = shortHex =>
+  shortHex[0] == '#' ? ('#' + shortHex.slice(1).split('').map(x => x+x).join('')) :
+    ('#' + shortHex.split('').map(x => x+x).join(''));
+// convertHex('#03f') -> '#0033ff'
+// convertHex('05a') -> '#0055aa'
+```
+
+[⬆ back to top](#table-of-contents)
+
 ### Escape regular expression
 
 Use `replace()` to escape special characters.
@@ -1300,17 +1391,6 @@ const rgbToHex = (r, g, b) => ((r << 16) + (g << 8) + b).toString(16).padStart(6
 
 [⬆ back to top](#table-of-contents)
 
-### Swap values of two variables
-
-Use array destructuring to swap values between two variables.
-
-```js
-[varA, varB] = [varB, varA];
-// [x, y] = [y, x]
-```
-
-[⬆ back to top](#table-of-contents)
-
 ### URL parameters
 
 Use `match()` with an appropriate regular expression to get all key-value pairs, `Array.reduce()` to map and combine them into a single object.
diff --git a/snippets/3-digit-hexcode-to-6-digit-hexcode.md b/snippets/3-digit-hexcode-to-6-digit-hexcode.md
new file mode 100644
index 000000000..a138b34bb
--- /dev/null
+++ b/snippets/3-digit-hexcode-to-6-digit-hexcode.md
@@ -0,0 +1,11 @@
+### 3-digit hexcode to 6-digit hexcode
+
+Use `Array.map()`, `split()` and `Array.join()` to join the mapped array for converting a three-digit RGB notated hexadecimal colorcode to the six-digit form.
+
+```js
+const convertHex = shortHex =>
+  shortHex[0] == '#' ? ('#' + shortHex.slice(1).split('').map(x => x+x).join('')) :
+    ('#' + shortHex.split('').map(x => x+x).join(''));
+// convertHex('#03f') -> '#0033ff'
+// convertHex('05a') -> '#0055aa'
+```
diff --git a/snippets/array-concatenation.md b/snippets/array-concatenation.md
index 40bf43c29..4c337c9e9 100644
--- a/snippets/array-concatenation.md
+++ b/snippets/array-concatenation.md
@@ -1,8 +1,8 @@
 ### Array concatenation
 
-Use `Array.concat()` to concatenate an array with any additional arrays and/or values, specified in `args`.
+Use Array spread operators (`...`) to concatenate an array with any additional arrays and/or values, specified in `args`.
 
 ```js
-const ArrayConcat = (arr, ...args) => [].concat(arr, ...args); 
-// ArrayConcat([1], [1, 2, 3, [4]]) -> [1, 2, 3, [4]]
+const ArrayConcat = (arr, ...args) => [...arr,...args]; 
+// ArrayConcat([1], [1, 2, 3, [4]]) -> [1, 1, 2, 3, [4]]
 ```
diff --git a/snippets/array-without.md b/snippets/array-without.md
index dd657fe2a..b5b41aee8 100644
--- a/snippets/array-without.md
+++ b/snippets/array-without.md
@@ -1,9 +1,9 @@
 ### Array without
 
-Use `Array.filter()` to create an array excluding all given values.
+Use `Array.filter()` to create an array excluding(using `!Array.includes()`) all given values.
 
 ```js
-const without = (arr, ...args) => arr.filter(v => args.indexOf(v) === -1);
-// without[2, 1, 2, 3], 1, 2) -> [3]
+const without = (arr, ...args) => arr.filter(v => !args.includes(v));
+// without([2, 1, 2, 3], 1, 2) -> [3]
 // without([2, 1, 2, 3, 4, 5, 5, 5, 3, 2, 7, 7], 3, 1, 5, 2) -> [ 4, 7, 7 ]
 ```
diff --git a/snippets/array-zip.md b/snippets/array-zip.md
index 6c9a2491b..5c3193605 100644
--- a/snippets/array-zip.md
+++ b/snippets/array-zip.md
@@ -6,7 +6,7 @@ If lengths of the argument-arrays vary, `undefined` is used where no value could
 
 ```js
 const zip = (...arrays) => {
-  const maxLength = Math.max.apply(null, arrays.map(a => a.length));
+  const maxLength = Math.max(...arrays.map(x => x.length));
   return Array.from({length: maxLength}).map((_, i) => {
    return Array.from({length: arrays.length}, (_, k) => arrays[k][i]);
   })
diff --git a/snippets/clean-JSON-object.md b/snippets/clean-JSON-object.md
new file mode 100644
index 000000000..241f6ce09
--- /dev/null
+++ b/snippets/clean-JSON-object.md
@@ -0,0 +1,21 @@
+### Clean JSON object
+
+Use `Object.keys()` method to loop over given json object and deleting keys that are not `include`d in given array.
+also if you give it a special key(`childIndicator`) it will search deeply inside it to apply function to inner objects too.
+
+```js
+const cleanObj = (obj, keysToKeep = [], childIndicator) => {
+  Object.keys(obj).forEach(key => {
+    if (key === childIndicator) {
+      cleanObj(obj[key], keysToKeep, childIndicator);
+    } else if (!keysToKeep.includes(key)) {
+      delete obj[key];
+    }
+  })
+}
+/*
+  testObj = {a: 1, b: 2, children: {a: 1, b: 2}}
+  cleanObj(testObj, ["a"],"children")
+  console.log(testObj)// { a: 1, children : { a: 1}}
+*/
+```
diff --git a/snippets/compose-functions.md b/snippets/compose-functions.md
new file mode 100644
index 000000000..d61c9f3b6
--- /dev/null
+++ b/snippets/compose-functions.md
@@ -0,0 +1,14 @@
+### Compose functions
+
+Use `Array.reduce()` to perform right-to-left function composition.
+The last (rightmost) function can accept one or more arguments; the remaining functions must be unary.
+
+```js
+const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)));
+/*
+const add5 = x => x + 5
+const multiply = (x, y) => x * y
+const multiplyAndAdd5 = compose(add5, multiply)
+multiplyAndAdd5(5, 2) -> 15
+*/
+```
\ No newline at end of file
diff --git a/snippets/initialize-array-with-range.md b/snippets/initialize-array-with-range.md
index def23fb9c..082325699 100644
--- a/snippets/initialize-array-with-range.md
+++ b/snippets/initialize-array-with-range.md
@@ -5,6 +5,6 @@ You can omit `start` to use a default value of `0`.
 
 ```js
 const initializeArrayRange = (end, start = 0) =>
-  Array.apply(null, Array(end - start)).map((v, i) => i + start);
+  Array.from({ length: end - start }).map((v, i) => i + start);
 // initializeArrayRange(5) -> [0,1,2,3,4]
 ```
diff --git a/snippets/json-to-date.md b/snippets/json-to-date.md
index 1b02232d9..c1a260927 100644
--- a/snippets/json-to-date.md
+++ b/snippets/json-to-date.md
@@ -1,10 +1,11 @@
-### Convert JSON to date
+### JSON to date
 
-Converts dates coming from ajax as JSON to readable format `dd/mm/yyyy`
+Use `Date()`, to convert dates in JSON format to readable format (`dd/mm/yyyy`).
 
 ```js
 const jsonToDate = arr => {
-const dt = new Date(parseInt(arr.toString().substr(6)));
-return `${ dt.getDate() }/${ dt.getMonth() + 1 }/${ dt.getFullYear() }`};
+  const dt = new Date(parseInt(arr.toString().substr(6)));
+  return `${ dt.getDate() }/${ dt.getMonth() + 1 }/${ dt.getFullYear() }`
+};
 // jsonToDate(/Date(1489525200000)/) -> "14/3/2017"
 ```
diff --git a/snippets/pipe.md b/snippets/pipe-functions.md
similarity index 73%
rename from snippets/pipe.md
rename to snippets/pipe-functions.md
index e5136777b..6e34e1063 100644
--- a/snippets/pipe.md
+++ b/snippets/pipe-functions.md
@@ -1,6 +1,6 @@
-### Pipe
+### Pipe functions
 
-Use `Array.reduce()` to perform left-to-right function composition.
+Use `Array.reduce()` with the spread operator (`...`) to perform left-to-right function composition.
 The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
 
 ```js
diff --git a/snippets/read-file-as-array-of-lines.md b/snippets/read-file-as-array-of-lines.md
new file mode 100644
index 000000000..c64b61c6f
--- /dev/null
+++ b/snippets/read-file-as-array-of-lines.md
@@ -0,0 +1,19 @@
+### Read file as array of lines
+
+Use `readFileSync` function in `fs` node package to create a `Buffer` from a file.
+convert buffer to string using `toString(encoding)` function.
+creating an array from contents of file by `split`ing file content line by line(each `\n`).
+
+  ```js
+const fs = require('fs');
+const readFileToArray = filename => fs.readFileSync(filename).toString('UTF8').split('\n');
+/*
+  contents of test.txt :
+    line1
+    line2
+    line3
+    ___________________________
+  let arr = readFileToArray('test.txt')
+  console.log(arr) // -> ['line1', 'line2', 'line3']
+ */
+```
diff --git a/snippets/swap-values-of-two-variables.md b/snippets/swap-values-of-two-variables.md
deleted file mode 100644
index bb2f67150..000000000
--- a/snippets/swap-values-of-two-variables.md
+++ /dev/null
@@ -1,8 +0,0 @@
-### Swap values of two variables
-
-Use array destructuring to swap values between two variables.
-
-```js
-[varA, varB] = [varB, varA];
-// [x, y] = [y, x]
-```
diff --git a/snippets/take-every-nth-element.md b/snippets/take-every-nth-element.md
new file mode 100644
index 000000000..8db496353
--- /dev/null
+++ b/snippets/take-every-nth-element.md
@@ -0,0 +1,8 @@
+### Take every nth element
+
+Use `Array.filter()` to create a new array that contains every nth element of a given array.
+
+```js
+const everynth = (arr, nth) => arr.filter((e, i) => i % nth === 0);
+// everynth([1,2,3,4,5,6], 2) -> [ 1, 3, 5 ]
+```
diff --git a/snippets/write-json-to-file.md b/snippets/write-json-to-file.md
index 17de5a44e..587e5f0f1 100644
--- a/snippets/write-json-to-file.md
+++ b/snippets/write-json-to-file.md
@@ -1,4 +1,4 @@
-### Write a JSON to a file
+### Write JSON to file
 
 Use `fs.writeFile()`, template literals and `JSON.stringify()` to write a `json` object to a `.json` file.
 
diff --git a/tag_database b/tag_database
index 3acb709f1..9f1b18f46 100644
--- a/tag_database
+++ b/tag_database
@@ -1,3 +1,4 @@
+3-digit-hexcode-to-6-digit-hexcode:utility
 anagrams-of-string-(with-duplicates):string
 array-concatenation:array
 array-difference:array
@@ -15,8 +16,10 @@ capitalize-first-letter:string
 chain-asynchronous-functions:function
 check-for-palindrome:string
 chunk-array:array
+clean-JSON-object:object
 collatz-algorithm:math
 compact:array
+compose-functions:function
 count-occurrences-of-a-value-in-array:array
 current-URL:browser
 curry:function
@@ -62,11 +65,12 @@ object-to-key-value-pairs:object
 ordinal-suffix-of-number:utility
 percentile:math
 pick:array
-pipe:function
+pipe-functions:function
 powerset:math
 promisify:function
 random-integer-in-range:utility
 random-number-in-range:utility
+read-file-as-array-of-lines:node
 redirect-to-URL:browser
 reverse-a-string:string
 RGB-to-hexadecimal:utility
@@ -81,8 +85,8 @@ sort-characters-in-string-(alphabetical):string
 speech-synthesis-(experimental):media
 standard-deviation:math
 sum-of-array-of-numbers:array
-swap-values-of-two-variables:utility
 tail-of-list:array
+take-every-nth-element:array
 take-right:array
 take:array
 truncate-a-string:string
@@ -92,4 +96,4 @@ UUID-generator:utility
 validate-email:utility
 validate-number:utility
 value-or-default:utility
-write-json-to-file:node
+write-JSON-to-file:node