Merge branch 'master' into master

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'
+```

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]]
 ```

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 ]
 ```

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]);
   })

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}}
+*/
+```

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
+*/
+```

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]
 ```

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"
 ```

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

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']
+ */
+```

snippets/swap-values-of-two-variables.md

@@ -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]
-```

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 ]
+```

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.