Merge branch 'master' into patch-1

snippets/RGB-to-hexadecimal.md

@@ -4,6 +4,6 @@ Convert each value to a hexadecimal string, using `toString(16)`, then `padStart
 Combine values using `join('')`.
 
 ```js
-var rgbToHex = (r, g, b) =>
+const rgbToHex = (r, g, b) =>
   [r,g,b].map( v => v.toString(16).padStart(2,'0')).join('');
 ```

snippets/URL-parameters.md

@@ -5,6 +5,6 @@ Combine all key-value pairs into a single object using `Object.assign()` and the
 Pass `location.search` as the argument to apply to the current `url`.
 
 ```js
-var getUrlParameters = url =>
+const getUrlParameters = url =>
   Object.assign(...url.match(/([^?=&]+)(=([^&]*))?/g).map(m => {[f,v] = m.split('='); return {[f]:v}}));
 ```

snippets/UUID-generator.md

@@ -3,7 +3,7 @@
 Use `crypto` API to generate a UUID, compliant with [RFC4122](https://www.ietf.org/rfc/rfc4122.txt) version 4.
 
 ```js
-var uuid = _ =>
+const uuid = _ =>
   ( [1e7]+-1e3+-4e3+-8e3+-1e11 ).replace( /[018]/g, c =>
     (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
   )

snippets/anagrams-of-string-(with-duplicates).md

@@ -6,7 +6,7 @@ Use `map()` to combine the letter with each partial anagram, then `reduce()` to
 Base cases are for string `length` equal to `2` or `1`.
 
 ```js
-var anagrams = s => {
+const anagrams = s => {
   if(s.length <= 2)  return s.length === 2 ? [s, s[1] + s[0]] : [s];
   return s.split('').reduce( (a,l,i) => {
     anagrams(s.slice(0,i) + s.slice(i+1)).map( v => a.push(l+v) );

snippets/average-of-array-of-numbers.md

@@ -3,6 +3,6 @@
 Use `reduce()` to add each value to an accumulator, initialized with a value of `0`, divide by the `length` of the array.
 
 ```js
-var average = arr =>
+const average = arr =>
   arr.reduce( (acc , val) => acc + val, 0) / arr.length;
 ```

snippets/capitalize-first-letter-of-every-word.md

@@ -0,0 +1,7 @@
+### Capitalize first letter of every word
+
+Use `replace()` to match the first character of each word and `toUpperCase()` to capitalize it.
+
+```js
+const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperCase());
+```

snippets/capitalize-first-letter.md

@@ -1,7 +1,9 @@
 ### Capitalize first letter
 
-Use `toUpperCase()` to capitalize first letter, `slice(1)` to get the rest of the string.
+Use `slice(0,1)` and `toUpperCase()` to capitalize first letter, `slice(1)` to get the rest of the string.
+Omit the `lowerRest` parameter to keep the rest of the string intact, or set it to `true` to convert to lower case.
 
 ```js
-var capitalize = str => str[0].toUpperCase() + str.slice(1);
+const capitalize = (str, lowerRest = false) =>
+  str.slice(0, 1).toUpperCase() + (lowerRest? str.slice(1).toLowerCase() : str.slice(1));
 ```

snippets/count-occurrences-of-a-value-in-array.md

@@ -1,7 +1,7 @@
 ### Count occurrences of a value in array
 
-Use `filter()` to create an array containing only the items with the specified value, count them using `length`.
+Use `reduce()` to increment a counter each time you encounter the specific value inside the array.
 
 ```js
-var countOccurrences = (arr, value) => arr.filter(v => v === value).length;
+const countOccurrences = (arr, value) => arr.reduce((a, v) => v===value ? a + 1 : a + 0, 0);
 ```

snippets/current-URL.md

@@ -3,5 +3,5 @@
 Use `window.location.href` to get current URL.
 
 ```js
-var currentUrl = _ => window.location.href;
+const currentUrl = _ => window.location.href;
 ```

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
-var curry = f =>
+const curry = f =>
   (...args) =>
     args.length >= f.length ? f(...args) : (...otherArgs) => curry(f)(...args, ...otherArgs)
 ```

snippets/difference-between-arrays.md

@@ -1,8 +1,7 @@
 ### Difference between arrays
 
-Use `filter()` to remove values that are part of `values`, determined using `indexOf()`.
+Use `filter()` to remove values that are part of `values`, determined using `includes()`.
 
 ```js
-var difference = (arr, values) =>
-  arr.filter(v => values.indexOf(v) === -1);
+const difference = (arr, values) => arr.filter(v => !values.includes(v));
 ```

snippets/distance-between-two-points.md

@@ -1,8 +1,7 @@
 ### Distance between two points
 
-Use `Math.pow()` and `Math.sqrt()` to calculate the Euclidean distance between two points.
+Use `Math.hypot()` to calculate the Euclidean distance between two points.
 
 ```js
-var distance = x0, y0, x1, y1 =>
-  Math.sqrt(Math.pow(x1-x0, 2) + Math.pow(y1 - y0, 2))
+const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0, y1 - y0);
 ```

snippets/escape-regular-expression.md

@@ -3,7 +3,7 @@
 Use `replace()` to escape special characters.
 
 ```js
-var escapeRegExp = s =>
+const escapeRegExp = s =>
   s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
 }
 ```

snippets/even-or-odd-number.md

@@ -4,5 +4,5 @@ Use `Math.abs()` to extend logic to negative numbers, check using the modulo (`%
 Return `true` if the number is even, `false` if the number is odd.
 
 ```js
-var isEven = num => Math.abs(num) % 2 === 0;
+const isEven = num => Math.abs(num) % 2 === 0;
 ```

snippets/factorial.md

@@ -1,8 +1,9 @@
 ### Factorial
 
-Create an array of length `n+1`, use `reduce()` to get the product of every value in the given range, utilizing the index of each element.
+Use recursion.
+If `n` is less than or equal to `1`, return `1`.
+Otherwise, return the product of `n` and the factorial of `n - 1`.
 
 ```js
-var factorial = n =>
-  Array.apply(null, [1].concat(Array(n))).reduce( (a, _, i) => a * i || 1 , 1);
+const factorial = n => n <= 1 ? 1 : n * factorial(n - 1)
 ```

snippets/fibonacci-array-generator.md

@@ -4,7 +4,7 @@ Create an empty array of the specific length, initializing the first two values
 Use `reduce()` to add values into the array, using the sum of the last two values, except for the first two.
 
 ```js
-var fibonacci = n =>
+const fibonacci = n =>
   Array.apply(null, [0,1].concat(Array(n-2))).reduce(
     (acc, val, i) => {
       acc.push( i>1 ? acc[i-1]+acc[i-2] : val);

snippets/filter-out-non-uniqe-values-in-an-array.md

@@ -0,0 +1,8 @@
+### Filter out non-unique values in an array
+
+Use `Array.filter()` for an array containing only the unique values.
+
+```js
+const unique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i));
+// unique([1,2,2,3,4,4,5]) -> [1,3,5]
+```

snippets/flatten-array.md

@@ -4,6 +4,6 @@ Use recursion.
 Use `reduce()` to get all elements that are not arrays, flatten each element that is an array.
 
 ```js
-var flatten = arr =>
+const flatten = arr =>
   arr.reduce( (a, v) => a.concat( Array.isArray(v) ? flatten(v) : v ), []);
 ```

snippets/get-scroll-position.md

@@ -0,0 +1,11 @@
+## Get scroll position
+
+Use `pageXOffset` and `pageYOffset` if they are defined, otherwise `scrollLeft` and `scrollTop`.
+You can omit `el` to use a default value of `window`.
+
+```js
+const getScrollPos = (el = window) =>
+  ( {x: (el.pageXOffset !== undefined) ? el.pageXOffset : el.scrollLeft,
+   y: (el.pageYOffset !== undefined) ? el.pageYOffset : el.scrollTop} );
+// getScrollPos() -> {x: 0, y: 200}
+```

snippets/greatest-common-divisor-(GCD).md

@@ -5,5 +5,5 @@ Base case is when `y` equals `0`. In this case, return `x`.
 Otherwise, return the GCD of `y` and the remainder of the division `x/y`.
 
 ```js
-var gcd = (x , y) => !y ? x : gcd(y, x % y);
+const gcd = (x , y) => !y ? x : gcd(y, x % y);
 ```

snippets/head-of-list.md

@@ -3,5 +3,5 @@
 Return `arr[0]`.
 
 ```js
-var head = arr => arr[0];
+const head = arr => arr[0];
 ```

snippets/initial-of-list.md

@@ -3,5 +3,5 @@
 Return `arr.slice(0,-1)`.
 
 ```js
-var initial = arr => arr.slice(0,-1);
+const initial = arr => arr.slice(0,-1);
 ```

snippets/initialize-array-with-range.md

@@ -4,6 +4,6 @@ Use `Array(end-start)` to create an array of the desired length, `map()` to fill
 You can omit `start` to use a default value of `0`.
 
 ```js
-var initializeArrayRange = (end, start = 0) =>
+const initializeArrayRange = (end, start = 0) =>
   Array.apply(null, Array(end-start)).map( (v,i) => i + start );
 ```

snippets/initialize-array-with-values.md

@@ -4,6 +4,6 @@ Use `Array(n)` to create an array of the desired length, `fill(v)` to fill it wi
 You can omit `v` to use a default value of `0`.
 
 ```js
-var initializeArray = (n, v = 0) =>
+const initializeArray = (n, v = 0) =>
   Array(n).fill(v);
 ```

snippets/last-of-list.md

@@ -3,5 +3,5 @@
 Return `arr.slice(-1)[0]`.
 
 ```js
-var initial = arr => arr.slice(-1)[0];
+const last = arr => arr.slice(-1)[0];
 ```

snippets/measure-time-taken-by-function.md

@@ -4,7 +4,7 @@ Use `performance.now()` to get start and end time for the function, `console.log
 First argument is the function name, subsequent arguments are passed to the function.
 
 ```js
-var timeTaken = (f,...args) => {
+const timeTaken = (f,...args) => {
   var t0 = performance.now(), r = f(...args);
   console.log(performance.now() - t0);
   return r;

snippets/object-from-key-value-pairs.md

@@ -3,5 +3,5 @@
 Use `Array.reduce()` to create and combine key-value pairs.
 
 ```js
-const objectFromPairs = arr => arr => arr.reduce((a,b) => { a[b[0]] = b[1]; return a;}, {})
+const objectFromPairs = arr => arr => arr.reduce((a,b) => { a[b[0]] = b[1]; return a;}, {});
 ```

snippets/powerset.md

@@ -1,8 +1,8 @@
 ### Powerset
 
-Use `reduce()` combined with `map()` to iterate over elements and combine into an array containing all combinations. 
+Use `reduce()` combined with `map()` to iterate over elements and combine into an array containing all combinations.
 
 ```js
-var powerset = arr =>
+const powerset = arr =>
   arr.reduce( (a,v) => a.concat(a.map( r => [v].concat(r) )), [[]]);
 ```

snippets/random-number-in-range.md

@@ -3,5 +3,5 @@
 Use `Math.random()` to generate a random value, map it to the desired range using multiplication.
 
 ```js
-var randomInRange = (min, max) => Math.random() * (max - min) + min;
+const randomInRange = (min, max) => Math.random() * (max - min) + min;
 ```

snippets/randomize-order-of-array.md

@@ -3,5 +3,5 @@
 Use `sort()` to reorder elements, utilizing `Math.random()` to randomize the sorting.
 
 ```js
-var randomizeOrder = arr => arr.sort( (a,b) => Math.random() >= 0.5 ? -1 : 1)
+const randomizeOrder = arr => arr.sort( (a,b) => Math.random() >= 0.5 ? -1 : 1)
 ```

snippets/redirect-to-url.md

@@ -4,6 +4,6 @@ Use `window.location.href` or `window.location.replace()` to redirect to `url`.
 Pass a second argument to simulate a link click (`true` - default) or an HTTP redirect (`false`).
 
 ```js
-var redirect = (url, asLink = true) =>
+const redirect = (url, asLink = true) =>
   asLink ? window.location.href = url : window.location.replace(url);
 ```

snippets/reverse-a-string.md

@@ -0,0 +1,8 @@
+### Reverse a string
+
+Use array destructuring and `Array.reverse()` to reverse the order of the characters in the string.
+Combine characters to get a string using `join('')`.
+
+```js
+const reverseString = str => [...str].reverse().join('');
+```

snippets/scroll-to-top.md

@@ -1,11 +1,11 @@
 ### Scroll to top
 
 Get distance from top using `document.documentElement.scrollTop` or `document.body.scrollTop`.
-Scroll by a fraction of the distance from top. Use `window.requestFrame()` to animate the scrolling.
+Scroll by a fraction of the distance from top. Use `window.requestAnimationFrame()` to animate the scrolling.
 
 ```js
-var scrollToTop = _ => {
-  var c = document.documentElement.scrollTop || document.body.scrollTop;
+const scrollToTop = _ => {
+  const c = document.documentElement.scrollTop || document.body.scrollTop;
   if(c > 0) {
     window.requestAnimationFrame(scrollToTop);
     window.scrollTo(0, c - c/8);

snippets/similarity-between-arrays.md

@@ -1,8 +1,7 @@
 ### Similarity between arrays
 
-Use `filter()` to remove values that are not part of `values`, determined using `indexOf()`.
+Use `filter()` to remove values that are not part of `values`, determined using `includes()`.
 
 ```js
-var difference = (arr, values) =>
-  arr.filter(v => values.indexOf(v) !== -1);
+const difference = (arr, values) => arr.filter(v => values.includes(v));
 ```

snippets/sort-characters-in-string-(alphabetical).md

@@ -3,6 +3,6 @@
 Split the string using `split('')`, `sort()` utilizing `localeCompare()`, recombine using `join('')`.
 
 ```js
-var sortCharactersInString = str =>
+const sortCharactersInString = str =>
   str.split('').sort( (a,b) => a.localeCompare(b) ).join('');
 ```

snippets/sum-of-array-of-numbers.md

@@ -3,6 +3,6 @@
 Use `reduce()` to add each value to an accumulator, initialized with a value of `0`.
 
 ```js
-var sum = arr =>
+const sum = arr =>
   arr.reduce( (acc , val) => acc + val, 0);
 ```

snippets/tail-of-list.md

@@ -3,5 +3,5 @@
 Return `arr.slice(1)`.
 
 ```js
-var tail = arr => arr.slice(1);
+const tail = arr => arr.slice(1);
 ```

snippets/unique-values-of-array.md

@@ -1,13 +1,8 @@
 ### Unique values of array
 
-Use `reduce()` to accumulate all unique values in an array.
-Check if each value has already been added, using `indexOf()` on the accumulator array.
+Use ES6 `Set` and the `...rest` operator to discard all duplicated values.
 
 ```js
-var uniqueValues = arr =>
-  arr.reduce( (acc, val) => {
-    if(acc.indexOf(val) === -1)
-      acc.push(val);
-      return acc;
-  }, []);
+const unique = arr => [...new Set(arr)];
+// unique([1,2,2,3,4,4,5]) -> [1,2,3,4,5]
 ```

snippets/validate-number.md

@@ -4,5 +4,5 @@ Use `!isNaN` in combination with `parseFloat()` to check if the argument is a nu
 Use `isFinite()` to check if the number is finite.
 
 ```js
-var validateNumber = n => !isNaN(parseFloat(n)) && isFinite(n);
+const validateNumber = n => !isNaN(parseFloat(n)) && isFinite(n);
 ```