Update snippet descriptions

snippets/createElement.md

@@ -6,8 +6,8 @@ tags: browser,beginner
 Creates an element from a string (without appending it to the document).
 If the given string contains multiple elements, only the first one will be returned.
 
-- Use `document.createElement()` to create a new element.
-- Set its `innerHTML` to the string supplied as the argument.
+- Use `Document.createElement()` to create a new element.
+- Use `Element.innerHTML` to set its inner HTML to the string supplied as the argument.
 - Use `ParentNode.firstElementChild` to return the element version of the string.
 
 ```js

snippets/curry.md

@@ -7,7 +7,7 @@ Curries a function.
 
 - Use recursion.
 - If the number of provided arguments (`args`) is sufficient, call the passed function `fn`.
-- Otherwise, return a curried function `fn` that expects the rest of the arguments.
+- Otherwise, use `Function.prototype.bind()` to return a curried function `fn` that expects the rest of the arguments.
 - If you want to curry a function that accepts a variable number of arguments (a variadic function, e.g. `Math.min()`), you can optionally pass the number of arguments to the second parameter `arity`.
 
 ```js

snippets/dayOfYear.md

@@ -3,9 +3,10 @@ title: dayOfYear
 tags: date,beginner
 ---
 
-Gets the day of the year from a `Date` object.
+Gets the day of the year (number in the range 1-366) from a `Date` object.
 
-- Use `new Date()` and `Date.prototype.getFullYear()` to get the first day of the year as a `Date` object, subtract it from the provided `date` and divide with the milliseconds in each day to get the result.
+- Use `new Date()` and `Date.prototype.getFullYear()` to get the first day of the year as a `Date` object.
+- Subtract the first day of the year from `date` and divide with the milliseconds in each day to get the result.
 - Use `Math.floor()` to appropriately round the resulting day count to an integer.
 
 ```js

snippets/daysAgo.md

@@ -1,9 +1,9 @@
 ---
 title: daysAgo
-tags: date,intermediate
+tags: date,beginner
 ---
 
-Returns the date of `n` days ago from today as a string representation.
+Calculates the date of `n` days ago from today as a string representation.
 
 - Use `new Date()` to get the current date, `Math.abs()` and `Date.getDate()` to update the date accordingly and set to the result using `Date.setDate()`.
 - Use `Date.prototype.toISOString()` to return a string in `yyyy-mm-dd` format.

snippets/daysFromNow.md

@@ -3,7 +3,7 @@ title: daysFromNow
 tags: date,beginner
 ---
 
-Returns the date of `n` days from today as a string representation.
+Calculates the date of `n` days from today as a string representation.
 
 - Use `new Date()` to get the current date, `Math.abs()` and `Date.getDate()` to update the date accordingly and set to the result using `Date.setDate()`.
 - Use `Date.prototype.toISOString()` to return a string in `yyyy-mm-dd` format.
@@ -13,7 +13,7 @@ const daysFromNow = n => {
   let d = new Date();
   d.setDate(d.getDate() + Math.abs(n));
   return d.toISOString().split('T')[0];
-}
+};
 ```
 
 ```js

snippets/debounce.md

@@ -7,7 +7,7 @@ Creates a debounced function that delays invoking the provided function until at
 
 - Each time the debounced function is invoked, clear the current pending timeout with `clearTimeout()` and use `setTimeout()` to create a new timeout that delays invoking the function until at least `ms` milliseconds has elapsed.
 - Use `Function.prototype.apply()` to apply the `this` context to the function and provide the necessary arguments.
-- Omit the second argument, `ms`, to set the timeout at a default of 0 ms.
+- Omit the second argument, `ms`, to set the timeout at a default of `0` ms.
 
 ```js
 const debounce = (fn, ms = 0) => {

snippets/debouncePromise.md

@@ -11,7 +11,7 @@ All promises returned during this time will return the same data.
 - Create a new `Promise` and add its `resolve` and `reject` callbacks to the `pending` promises stack.
 - When `setTimeout` is called, copy the current stack (as it can change between the provided function call and its resolution), clear it and call the provided function.
 - When the provided function resolves/rejects, resolve/reject all promises in the stack (copied when the function was called) with the returned data.
-- Omit the second argument, `ms`, to set the timeout at a default of 0 ms.
+- Omit the second argument, `ms`, to set the timeout at a default of `0` ms.
 
 ```js
 const debouncePromise = (fn, ms = 0) => {

snippets/deepFreeze.md

@@ -21,8 +21,8 @@ const deepFreeze = obj => {
 ```js
 'use strict';
 
-const o = deepFreeze([1, [2, 3]]);
+const val = deepFreeze([1, [2, 3]]);
 
-o[0] = 3; // not allowed
-o[1][0] = 4; // not allowed as well
+val[0] = 3; // not allowed
+val[1][0] = 4; // not allowed as well
 ```

snippets/deepGet.md

@@ -3,11 +3,11 @@ title: deepGet
 tags: object,intermediate
 ---
 
-Returns the target value in a nested JSON object, based on the `keys` array.
+Gets the target value in a nested JSON object, based on the `keys` array.
 
 - Compare the keys you want in the nested JSON object as an `Array`.
-- Use `Array.prototype.reduce()` to get value from nested JSON object one by one.
-- If the key exists in object, return target value, otherwise, return `null`.
+- Use `Array.prototype.reduce()` to get the values in the nested JSON object one by one.
+- If the key exists in the object, return the target value, otherwise return `null`.
 
 ```js
 const deepGet = (obj, keys) =>

snippets/defer.md

@@ -5,7 +5,7 @@ tags: function,intermediate
 
 Defers invoking a function until the current call stack has cleared.
 
-- Use `setTimeout()` with a timeout of 1ms to add a new event to the browser event queue and allow the rendering engine to complete its work.
+- Use `setTimeout()` with a timeout of `1` ms to add a new event to the event queue and allow the rendering engine to complete its work.
 - Use the spread (`...`) operator to supply the function with an arbitrary number of arguments.
 
 ```js

snippets/delay.md

@@ -3,13 +3,13 @@ title: delay
 tags: function,intermediate
 ---
 
-Invokes the provided function after `wait` milliseconds.
+Invokes the provided function after `ms` milliseconds.
 
 - Use `setTimeout()` to delay execution of `fn`.
 - Use the spread (`...`) operator to supply the function with an arbitrary number of arguments.
 
 ```js
-const delay = (fn, wait, ...args) => setTimeout(fn, wait, ...args);
+const delay = (fn, ms, ...args) => setTimeout(fn, ms, ...args);
 ```
 
 ```js

snippets/detectDeviceType.md

@@ -1,11 +1,11 @@
 ---
 title: detectDeviceType
-tags: browser,intermediate
+tags: browser,regexp,intermediate
 ---
 
-Detects whether the website is being opened in a mobile device or a desktop/laptop.
+Detects whether the page is being viewed on a mobile device or a desktop.
 
-- Use a regular expression to test the `navigator.userAgent` property to figure out if the device is a mobile device or a desktop/laptop.
+- Use a regular expression to test the `navigator.userAgent` property to figure out if the device is a mobile device or a desktop.
 
 ```js
 const detectDeviceType = () =>

snippets/difference.md

@@ -1,11 +1,12 @@
 ---
 title: difference
-tags: array,math,beginner
+tags: array,beginner
 ---
 
-Returns the difference between two arrays.
+Calculates the difference between two arrays, without filtering duplicate values.
 
-- Create a `Set` from `b`, then use `Array.prototype.filter()` on `a` to only keep values not contained in `b`.
+- Create a `Set` from `b` to get the unique values in `b`.
+- Use `Array.prototype.filter()` on `a` to only keep values not contained in `b`, using `Set.prototype.has()`.
 
 ```js
 const difference = (a, b) => {
@@ -15,5 +16,5 @@ const difference = (a, b) => {
 ```
 
 ```js
-difference([1, 2, 3], [1, 2, 4]); // [3]
+difference([1, 2, 3, 3], [1, 2, 4]); // [3, 3]
 ```

snippets/differenceWith.md

@@ -6,11 +6,14 @@ tags: array,intermediate
 Filters out all values from an array for which the comparator function does not return `true`.
 
 - Use `Array.prototype.filter()` and `Array.prototype.findIndex()` to find the appropriate values.
+- Omit the last argument, `comp`, to use a default strict equality comparator.
 
 ```js
-const differenceWith = (arr, val, comp) => arr.filter(a => val.findIndex(b => comp(a, b)) === -1);
+const differenceWith = (arr, val, comp = (a, b) => a === b) =>
+  arr.filter(a => val.findIndex(b => comp(a, b)) === -1);
 ```
 
 ```js
 differenceWith([1, 1.2, 1.5, 3, 0], [1.9, 3, 0], (a, b) => Math.round(a) === Math.round(b)); // [1, 1.2]
+differenceWith([1, 1.2, 1.3], [1, 1.3, 1.5]); // [1.2]
 ```

snippets/dig.md

@@ -3,10 +3,11 @@ title: dig
 tags: object,recursion,intermediate
 ---
 
-Returns the target value in a nested JSON object, based on the given key.
+Gets the target value in a nested JSON object, based on the given key.
 
 - Use the `in` operator to check if `target` exists in `obj`.
-- If found, return the value of `obj[target]`, otherwise use `Object.values(obj)` and `Array.prototype.reduce()` to recursively call `dig` on each nested object until the first matching key/value pair is found.
+- If found, return the value of `obj[target]`.
+- Otherwise use `Object.values(obj)` and `Array.prototype.reduce()` to recursively call `dig` on each nested object until the first matching key/value pair is found.
 
 ```js
 const dig = (obj, target) =>

snippets/distance.md

@@ -3,7 +3,7 @@ title: distance
 tags: math,beginner
 ---
 
-Returns the distance between two points.
+Calculates the distance between two points.
 
 - Use `Math.hypot()` to calculate the Euclidean distance between two points.
 
@@ -12,5 +12,5 @@ const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0, y1 - y0);
 ```
 
 ```js
-distance(1, 1, 2, 3); // 2.23606797749979
+distance(1, 1, 2, 3); // ~2.2361
 ```

snippets/dropRightWhile.md

@@ -3,10 +3,11 @@ title: dropRightWhile
 tags: array,intermediate
 ---
 
-Removes elements from the end of an array until the passed function returns `true`. Returns the remaining elements in the array.
+Removes elements from the end of an array until the passed function returns `true`.
+Returns the remaining elements in the array.
 
-- Loop through the array, using `Array.prototype.slice()` to drop the last element of the array until the returned value from the function is `true`.
-- Returns the remaining elements.
+- Loop through the array, using `Array.prototype.slice()` to drop the last element of the array until the value returned from `func` is `true`.
+- Return the remaining elements.
 
 ```js
 const dropRightWhile = (arr, func) => {

snippets/dropWhile.md

@@ -3,10 +3,11 @@ title: dropWhile
 tags: array,intermediate
 ---
 
-Removes elements in an array until the passed function returns `true`. Returns the remaining elements in the array.
+Removes elements in an array until the passed function returns `true`.
+Returns the remaining elements in the array.
 
-- Loop through the array, using `Array.prototype.slice()` to drop the first element of the array until the returned value from the function is `true`.
-- Returns the remaining elements.
+- Loop through the array, using `Array.prototype.slice()` to drop the first element of the array until the value returned from `func` is `true`.
+- Return the remaining elements.
 
 ```js
 const dropWhile = (arr, func) => {

snippets/either.md

@@ -3,7 +3,7 @@ title: either
 tags: function,logic,beginner
 ---
 
-Returns `true` if at least one function returns `true` for a given set of arguments, `false` otherwise.
+Checks if at least one function returns `true` for a given set of arguments.
 
 - Use the logical or (`||`) operator on the result of calling the two functions with the supplied `args`.
 

snippets/elementContains.md

@@ -3,9 +3,10 @@ title: elementContains
 tags: browser,intermediate
 ---
 
-Returns `true` if the `parent` element contains the `child` element, `false` otherwise.
+Checks if the `parent` element contains the `child` element.
 
-- Check that `parent` is not the same element as `child`, use `parent.contains(child)` to check if the `parent` element contains the `child` element.
+- Check that `parent` is not the same element as `child`.
+- Use `Node.contains()` to check if the `parent` element contains the `child` element.
 
 ```js
 const elementContains = (parent, child) => parent !== child && parent.contains(child);

snippets/elementIsFocused.md

@@ -1,11 +1,11 @@
 ---
 title: elementIsFocused
-tags: browser,intermediate
+tags: browser,beginner
 ---
 
-Returns `true` if the given element is focused, `false` otherwise.
+Checks if the given element is focused.
 
-- Use `document.activeElement` to determine if the given element is focused.
+- Use `Document.activeElement` to determine if the given element is focused.
 
 ```js
 const elementIsFocused = el => (el === document.activeElement);

snippets/elementIsVisibleInViewport.md

@@ -1,12 +1,11 @@
 ---
 title: elementIsVisibleInViewport
-tags: browser,advanced
+tags: browser,intermediate
 ---
 
-Returns `true` if the element specified is visible in the viewport, `false` otherwise.
+Checks if the element specified is visible in the viewport.
 
-- Use `Element.getBoundingClientRect()` and the `window.inner(Width|Height)` values
-- to determine if a given element is visible in the viewport.
+- Use `Element.getBoundingClientRect()` and the `window.inner(Width|Height)` values to determine if a given element is visible in the viewport.
 - Omit the second argument to determine if the element is entirely visible, or specify `true` to determine if it is partially visible.
 
 ```js

snippets/equals.md

@@ -7,7 +7,8 @@ Performs a deep comparison between two values to determine if they are equivalen
 
 - Check if the two values are identical, if they are both `Date` objects with the same time, using `Date.getTime()` or if they are both non-object values with an equivalent value (strict comparison).
 - Check if only one value is `null` or `undefined` or if their prototypes differ.
-- If none of the above conditions are met, use `Object.keys()` to check if both values have the same number of keys, then use `Array.prototype.every()` to check if every key in the first value exists in the second one and if they are equivalent by calling this method recursively.
+- If none of the above conditions are met, use `Object.keys()` to check if both values have the same number of keys.
+- Use `Array.prototype.every()` to check if every key in `a` exists in `b` and if they are equivalent by calling `equals()` recursively.
 
 ```js
 const equals = (a, b) => {

snippets/escapeHTML.md

@@ -5,7 +5,8 @@ tags: string,browser,regexp,intermediate
 
 Escapes a string for use in HTML.
 
-- Use `String.prototype.replace()` with a regexp that matches the characters that need to be escaped, using a callback function to replace each character instance with its associated escaped character using a dictionary (object).
+- Use `String.prototype.replace()` with a regexp that matches the characters that need to be escaped.
+- Use the callback function to replace each character instance with its associated escaped character using a dictionary (object).
 
 ```js
 const escapeHTML = str =>
@@ -23,5 +24,6 @@ const escapeHTML = str =>
 ```
 
 ```js
-escapeHTML('<a href="#">Me & you</a>'); // '&lt;a href=&quot;#&quot;&gt;Me &amp; you&lt;/a&gt;'
+escapeHTML('<a href="#">Me & you</a>'); 
+// '&lt;a href=&quot;#&quot;&gt;Me &amp; you&lt;/a&gt;'
 ```

snippets/everyNth.md

@@ -3,9 +3,9 @@ title: everyNth
 tags: array,beginner
 ---
 
-Returns every nth element in an array.
+Returns every `nth` element in an array.
 
-- Use `Array.prototype.filter()` to create a new array that contains every nth element of a given array.
+- Use `Array.prototype.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 === nth - 1);

snippets/factorial.md

@@ -8,7 +8,7 @@ Calculates the factorial of a number.
 - 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`.
-- Throws an exception if `n` is a negative number.
+- Throw a `TypeError` if `n` is a negative number.
 
 ```js
 const factorial = n =>

snippets/fahrenheitToCelsius.md

@@ -8,7 +8,7 @@ Converts Fahrenheit to Celsius.
 - Follows the conversion formula `C = (F - 32) * 5/9`.
 
 ```js
-const fahrenheitToCelsius = degrees => ((degrees - 32) * 5) / 9;
+const fahrenheitToCelsius = degrees => (degrees - 32) * 5 / 9;
 ```
 
 ```js

snippets/fibonacci.md

@@ -1,12 +1,12 @@
 ---
 title: fibonacci
-tags: math,beginner
+tags: math,intermediate
 ---
 
 Generates an array, containing the Fibonacci sequence, up until the nth term.
 
-- Create an empty array of the specific length, initializing the first two values (`0` and `1`).
-- Use `Array.prototype.reduce()` to add values into the array, using the sum of the last two values, except for the first two.
+- Use `Array.from()` to create an empty array of the specific length, initializing the first two values (`0` and `1`).
+- Use `Array.prototype.reduce()` and `Array.prototype.concat()` to add values into the array, using the sum of the last two values, except for the first two.
 
 ```js
 const fibonacci = n =>

snippets/filterNonUnique.md

@@ -3,9 +3,9 @@ title: filterNonUnique
 tags: array,beginner
 ---
 
-Filters out the non-unique values in an array.
+Returns an array with the non-unique values filtered out.
 
-- Use `Array.prototype.filter()` for an array containing only the unique values.
+- Use `Array.prototype.filter()` to create an array containing only the unique values.
 
 ```js
 const filterNonUnique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i));

snippets/filterNonUniqueBy.md

@@ -3,9 +3,9 @@ title: filterNonUniqueBy
 tags: array,intermediate
 ---
 
-Filters out the non-unique values in an array, based on a provided comparator function.
+Returns an array with the non-unique values filtered out, based on a provided comparator function.
 
-- Use `Array.prototype.filter()` and `Array.prototype.every()` for an array containing only the unique values, based on the comparator function, `fn`.
+- Use `Array.prototype.filter()` and `Array.prototype.every()` to create an array containing only the unique values, based on the comparator function, `fn`.
 - The comparator function takes four arguments: the values of the two elements being compared and their indexes.
 
 ```js

snippets/findKey.md

@@ -3,9 +3,10 @@ title: findKey
 tags: object,intermediate
 ---
 
-Returns the first key that satisfies the provided testing function. Otherwise `undefined` is returned.
+Returns the first key that satisfies the provided testing function.
+Otherwise `undefined` is returned.
 
-- Use `Object.keys(obj)` to get all the properties of the object, `Array.prototype.find()` to test the provided function for each key-value pair.
+- Use `Object.keys(obj)` to get all the properties of the object, `Array.prototype.find()` to test each key-value pair using `fn`.
 - The callback receives three arguments - the value, the key and the object.
 
 ```js
@@ -19,6 +20,6 @@ findKey(
     fred: { age: 40, active: false },
     pebbles: { age: 1, active: true }
   },
-  o => o['active']
+  x => x['active']
 ); // 'barney'
 ```

snippets/findLast.md

@@ -5,7 +5,8 @@ tags: array,beginner
 
 Returns the last element for which the provided function returns a truthy value.
 
-- Use `Array.prototype.filter()` to remove elements for which `fn` returns falsy values, `Array.prototype.pop()` to get the last one.
+- Use `Array.prototype.filter()` to remove elements for which `fn` returns falsy values.
+- Use `Array.prototype.pop()` to get the last element in the filtered array.
 
 ```js
 const findLast = (arr, fn) => arr.filter(fn).pop();

snippets/findLastIndex.md

@@ -6,8 +6,9 @@ tags: array,intermediate
 Returns the index of the last element for which the provided function returns a truthy value.
 
 - Use `Array.prototype.map()` to map each element to an array with its index and value.
-- Use `Array.prototype.filter()` to remove elements for which `fn` returns falsy values, `Array.prototype.pop()` to get the last one.
-- `-1` is the default value when not found.
+- Use `Array.prototype.filter()` to remove elements for which `fn` returns falsy values
+- Use `Array.prototype.pop()` to get the last element in the filtered array.
+- Return `-1` if there are no matching elements.
 
 ```js
 const findLastIndex = (arr, fn) =>

snippets/findLastKey.md

@@ -6,7 +6,8 @@ tags: object,intermediate
 Returns the last key that satisfies the provided testing function.
 Otherwise `undefined` is returned.
 
-- Use `Object.keys(obj)` to get all the properties of the object, `Array.prototype.reverse()` to reverse their order and `Array.prototype.find()` to test the provided function for each key-value pair.
+- Use `Object.keys(obj)` to get all the properties of the object.
+- Use `Array.prototype.reverse()` to reverse the order and `Array.prototype.find()` to test the provided function for each key-value pair.
 - The callback receives three arguments - the value, the key and the object.
 
 ```js
@@ -23,6 +24,6 @@ findLastKey(
     fred: { age: 40, active: false },
     pebbles: { age: 1, active: true }
   },
-  o => o['active']
+  x => x['active']
 ); // 'pebbles'
 ```

snippets/flatten.md

@@ -1,14 +1,14 @@
 ---
 title: flatten
-tags: array,intermediate
+tags: array,recursion,intermediate
 ---
 
 Flattens an array up to the specified depth.
 
-- Use recursion, decrementing `depth` by 1 for each level of depth.
+- Use recursion, decrementing `depth` by `1` for each level of depth.
 - Use `Array.prototype.reduce()` and `Array.prototype.concat()` to merge elements or arrays.
 - Base case, for `depth` equal to `1` stops recursion.
-- Omit the second argument, `depth` to flatten only to a depth of `1` (single flatten).
+- Omit the second argument, `depth`, to flatten only to a depth of `1` (single flatten).
 
 ```js
 const flatten = (arr, depth = 1) =>

snippets/flattenObject.md

@@ -1,9 +1,9 @@
 ---
 title: flattenObject
-tags: object,recursion,intermediate
+tags: object,recursion,advanced
 ---
 
-Flatten an object with the paths for keys.
+Flattens an object with the paths for keys.
 
 - Use recursion.
 - Use `Object.keys(obj)` combined with `Array.prototype.reduce()` to convert every leaf node to a flattened path node.