Performs left-to-right function composition for asynchronous functions.
Use Array.prototype.reduce() with the spread operator (...) to perform left-to-right function composition using Promise.then(). The functions can return a combination of: simple values, Promise's, or they can be defined as async ones returning through await. All functions must be unary.
const pipeAsyncFunctions = (...fns) => arg => fns.reduce((p, f) => p.then(f), Promise.resolve(arg)); -
const sum = pipeAsyncFunctions( +
+const sum = pipeAsyncFunctions( x => x + 1, x => new Promise(resolve => setTimeout(() => resolve(x + 2), 1000)), x => x + 3, async x => (await x) + 4 ); -(async () => { +(async() => { console.log(await sum(5)); // 15 (after one second) })();
Learn new ES6 JavaScript language features like arrow function, destructuring, generators & more to write cleaner and more productive, readable programs.
Performs left-to-right function composition.
Use Array.prototype.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.
const pipeFunctions = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args))); diff --git a/docs/index.html b/docs/index.html index c95dab963..23615fa84 100644 --- a/docs/index.html +++ b/docs/index.html @@ -407,12 +407,13 @@
Takes a predicate and array, like Array.prototype.filter(), but only keeps x if pred(x) === false.
const reject = (pred, array) => array.filter((...args) => !pred(...args));
reject(x => x % 2 === 0, [1, 2, 3, 4, 5]); // [1, 3, 5] reject(word => word.length > 4, ['Apple', 'Pear', 'Kiwi', 'Banana']); // ['Pear', 'Kiwi'] -
Removes elements from an array for which the given function returns false.
Use Array.prototype.filter() to find array elements that return truthy values and Array.prototype.reduce() to remove elements using Array.prototype.splice(). The func is invoked with three arguments (value, index, array).
const remove = (arr, func) => +
Removes elements from an array for which the given function returns false.
Use Array.prototype.filter() to find array elements that return truthy values and Array.prototype.reduce() to remove elements using Array.prototype.splice(). The func is invoked with three arguments (value, index, array).
+const remove = (arr, func) => Array.isArray(arr) ? arr.filter(func).reduce((acc, val) => { - arr.splice(arr.indexOf(val), 1); - return acc.concat(val); - }, []) + arr.splice(arr.indexOf(val), 1); + return acc.concat(val); + }, []) : [];
remove([1, 2, 3, 4], n => n % 2 === 0); // [2, 4]
Returns a random element from an array.
Use Math.random() to generate a random number, multiply it by length and round it off to the nearest whole number using Math.floor(). This method also works with strings.
const sample = arr => arr[Math.floor(Math.random() * arr.length)]; diff --git a/docs/math.html b/docs/math.html index 9d264ace2..5fee58fa0 100644 --- a/docs/math.html +++ b/docs/math.html @@ -149,11 +149,12 @@ For teams, each rating can adjusted based on own team's average rating vs. average rating of opposing team, with the score being added to their own individual rating by supplying it as the third argument. */ -
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.
const factorial = n => +
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.
+const factorial = n => n < 0 ? (() => { - throw new TypeError('Negative numbers are not allowed!'); - })() + throw new TypeError('Negative numbers are not allowed!'); + })() : n <= 1 ? 1 : n * factorial(n - 1); diff --git a/docs/object.html b/docs/object.html index 32ddb34ab..a668920c7 100644 --- a/docs/object.html +++ b/docs/object.html @@ -134,16 +134,17 @@ o[0] = 3; // not allowed o[1][0] = 4; // not allowed as well -
Deep maps an object keys.
Creates an object with the same values as the provided object and keys generated by running the provided function for each key.
Use Object.keys(obj) to iterate over the object's keys. Use Array.prototype.reduce() to create a new object with the same values and mapped keys using fn.
const deepMapKeys = (obj, f) => +
Deep maps an object keys.
Creates an object with the same values as the provided object and keys generated by running the provided function for each key.
Use Object.keys(obj) to iterate over the object's keys. Use Array.prototype.reduce() to create a new object with the same values and mapped keys using fn.
+const deepMapKeys = (obj, f) => Array.isArray(obj) ? obj.map(val => deepMapKeys(val, f)) : typeof obj === 'object' ? Object.keys(obj).reduce((acc, current) => { - const val = obj[current]; - acc[f(current)] = + const val = obj[current]; + acc[f(current)] = val !== null && typeof val === 'object' ? deepMapKeys(val, f) : (acc[f(current)] = val); - return acc; - }, {}) + return acc; + }, {}) : obj;
const obj = { foo: '1', @@ -174,13 +175,14 @@ o[1
Assigns default values for all properties in an object that are undefined.
Use Object.assign() to create a new empty object and copy the original one to maintain key order, use Array.prototype.reverse() and the spread operator ... to combine the default values from left to right, finally use obj again to overwrite properties that originally had a value.
const defaults = (obj, ...defs) => Object.assign({}, obj, ...defs.reverse(), obj);
defaults({ a: 1 }, { b: 2 }, { b: 6 }, { a: 3 }); // { a: 1, b: 2 } -
Returns 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.
const dig = (obj, target) => +
Returns 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.
+const dig = (obj, target) => target in obj ? obj[target] : Object.values(obj).reduce((acc, val) => { - if (acc !== undefined) return acc; - if (typeof val === 'object') return dig(val, target); - }, undefined); + if (acc !== undefined) return acc; + if (typeof val === 'object') return dig(val, target); + }, undefined);
const data = { level1: { level2: { diff --git a/snippets/deepMapKeys.md b/snippets/deepMapKeys.md index 970453bdc..e0223cb81 100644 --- a/snippets/deepMapKeys.md +++ b/snippets/deepMapKeys.md @@ -8,16 +8,17 @@ Use `Object.keys(obj)` to iterate over the object's keys. Use `Array.prototype.reduce()` to create a new object with the same values and mapped keys using `fn`. ```js + const deepMapKeys = (obj, f) => Array.isArray(obj) ? obj.map(val => deepMapKeys(val, f)) : typeof obj === 'object' ? Object.keys(obj).reduce((acc, current) => { - const val = obj[current]; - acc[f(current)] = + const val = obj[current]; + acc[f(current)] = val !== null && typeof val === 'object' ? deepMapKeys(val, f) : (acc[f(current)] = val); - return acc; - }, {}) + return acc; + }, {}) : obj; ``` diff --git a/snippets/dig.md b/snippets/dig.md index c97559833..a349ef2d3 100644 --- a/snippets/dig.md +++ b/snippets/dig.md @@ -6,13 +6,14 @@ 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. ```js + const dig = (obj, target) => target in obj ? obj[target] : Object.values(obj).reduce((acc, val) => { - if (acc !== undefined) return acc; - if (typeof val === 'object') return dig(val, target); - }, undefined); + if (acc !== undefined) return acc; + if (typeof val === 'object') return dig(val, target); + }, undefined); ``` ```js diff --git a/snippets/factorial.md b/snippets/factorial.md index 86ebe69b6..2266247b4 100644 --- a/snippets/factorial.md +++ b/snippets/factorial.md @@ -8,11 +8,12 @@ Otherwise, return the product of `n` and the factorial of `n - 1`. Throws an exception if `n` is a negative number. ```js + const factorial = n => n < 0 ? (() => { - throw new TypeError('Negative numbers are not allowed!'); - })() + throw new TypeError('Negative numbers are not allowed!'); + })() : n <= 1 ? 1 : n * factorial(n - 1); diff --git a/snippets/pipeAsyncFunctions.md b/snippets/pipeAsyncFunctions.md index 8c93add3b..61b850a39 100644 --- a/snippets/pipeAsyncFunctions.md +++ b/snippets/pipeAsyncFunctions.md @@ -11,13 +11,14 @@ const pipeAsyncFunctions = (...fns) => arg => fns.reduce((p, f) => p.then(f), Pr ``` ```js + const sum = pipeAsyncFunctions( x => x + 1, x => new Promise(resolve => setTimeout(() => resolve(x + 2), 1000)), x => x + 3, async x => (await x) + 4 ); -(async () => { +(async() => { console.log(await sum(5)); // 15 (after one second) })(); ``` diff --git a/snippets/remove.md b/snippets/remove.md index a8c472774..1c457d2d9 100644 --- a/snippets/remove.md +++ b/snippets/remove.md @@ -6,12 +6,13 @@ Use `Array.prototype.filter()` to find array elements that return truthy values The `func` is invoked with three arguments (`value, index, array`). ```js + const remove = (arr, func) => Array.isArray(arr) ? arr.filter(func).reduce((acc, val) => { - arr.splice(arr.indexOf(val), 1); - return acc.concat(val); - }, []) + arr.splice(arr.indexOf(val), 1); + return acc.concat(val); + }, []) : []; ``` diff --git a/test/_30s.js b/test/_30s.js index 670d752fc..0441f4c90 100644 --- a/test/_30s.js +++ b/test/_30s.js @@ -235,16 +235,17 @@ const deepFreeze = obj => prop => !(obj[prop] instanceof Object) || Object.isFrozen(obj[prop]) ? null : deepFreeze(obj[prop]) ) || Object.freeze(obj); + const deepMapKeys = (obj, f) => Array.isArray(obj) ? obj.map(val => deepMapKeys(val, f)) : typeof obj === 'object' ? Object.keys(obj).reduce((acc, current) => { - const val = obj[current]; - acc[f(current)] = + const val = obj[current]; + acc[f(current)] = val !== null && typeof val === 'object' ? deepMapKeys(val, f) : (acc[f(current)] = val); - return acc; - }, {}) + return acc; + }, {}) : obj; const defaults = (obj, ...defs) => Object.assign({}, obj, ...defs.reverse(), obj); const defer = (fn, ...args) => setTimeout(fn, 1, ...args); @@ -263,13 +264,14 @@ const differenceBy = (a, b, fn) => { return a.filter(x => !s.has(fn(x))); }; const differenceWith = (arr, val, comp) => arr.filter(a => val.findIndex(b => comp(a, b)) === -1); + const dig = (obj, target) => target in obj ? obj[target] : Object.values(obj).reduce((acc, val) => { - if (acc !== undefined) return acc; - if (typeof val === 'object') return dig(val, target); - }, undefined); + if (acc !== undefined) return acc; + if (typeof val === 'object') return dig(val, target); + }, undefined); const digitize = n => [...`${n}`].map(i => parseInt(i)); const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0, y1 - y0); const drop = (arr, n = 1) => arr.slice(n); @@ -338,11 +340,12 @@ const extendHex = shortHex => .split('') .map(x => x + x) .join(''); + const factorial = n => n < 0 ? (() => { - throw new TypeError('Negative numbers are not allowed!'); - })() + throw new TypeError('Negative numbers are not allowed!'); + })() : n <= 1 ? 1 : n * factorial(n - 1); @@ -985,12 +988,13 @@ const reducedFilter = (data, keys, fn) => }, {}) ); const reject = (pred, array) => array.filter((...args) => !pred(...args)); + const remove = (arr, func) => Array.isArray(arr) ? arr.filter(func).reduce((acc, val) => { - arr.splice(arr.indexOf(val), 1); - return acc.concat(val); - }, []) + arr.splice(arr.indexOf(val), 1); + return acc.concat(val); + }, []) : []; const removeNonASCII = str => str.replace(/[^\x20-\x7E]/g, ''); const renameKeys = (keysMap, obj) =>