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) })();
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/function.html b/docs/function.html index a50a88551..0de830c9d 100644 --- a/docs/function.html +++ b/docs/function.html @@ -121,7 +121,11 @@ console.log< console.log(freddyBound('hi', '!')); // 'hi fred!'
Chains asynchronous functions.
Loop through an array of functions containing asynchronous events, calling next when each asynchronous event has completed.
const chainAsync = fns => { let curr = 0; - const next = () => fns[curr++](next); + const last = fns[fns.length - 1]; + const next = () => { + const fn = fns[curr++]; + fn === last ? fn() : fn(next); + }; next(); };
chainAsync([ @@ -130,7 +134,11 @@ console.log< setTimeout(next, 1000); }, next => { - console.log('1 second'); + console.log('1 second'); + setTimeout(next, 1000); + }, + () => { + console.log('2 second'); } ]);
Performs right-to-left function composition.
Use Array.prototype.reduce() to perform right-to-left function composition. The last (rightmost) function can accept one or more arguments; the remaining functions must be unary.
const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args))); diff --git a/docs/index.html b/docs/index.html index 778ab9167..7137a28c8 100644 --- a/docs/index.html +++ b/docs/index.html @@ -405,12 +405,13 @@
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/snippets/chainAsync.md b/snippets/chainAsync.md index 5cb3c0985..ef0b2d851 100644 --- a/snippets/chainAsync.md +++ b/snippets/chainAsync.md @@ -9,9 +9,9 @@ const chainAsync = fns => { let curr = 0; const last = fns[fns.length - 1]; const next = () => { - const fn = fns[curr++] + const fn = fns[curr++]; fn === last ? fn() : fn(next); - } + }; next(); }; ``` 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 c0bb0070e..9bc7b0385 100644 --- a/test/_30s.js +++ b/test/_30s.js @@ -110,7 +110,11 @@ const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperC const castArray = val => (Array.isArray(val) ? val : [val]); const chainAsync = fns => { let curr = 0; - const next = () => fns[curr++](next); + const last = fns[fns.length - 1]; + const next = () => { + const fn = fns[curr++]; + fn === last ? fn() : fn(next); + }; next(); }; const chunk = (arr, size) => @@ -974,12 +978,13 @@ 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) =>