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/function.html b/docs/function.html index 45fa1af08..6865e9099 100644 --- a/docs/function.html +++ b/docs/function.html @@ -160,6 +160,7 @@ console.log< + const lengthIs4 = checkProp(l => l === 4, 'length'); lengthIs4([]); // false lengthIs4([1,2,3,4]); // true diff --git a/docs/index.html b/docs/index.html index 27620be47..76e0d2824 100644 --- a/docs/index.html +++ b/docs/index.html @@ -414,9 +414,9 @@
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 d16cfa3b5..1e48124c7 100644 --- a/docs/math.html +++ b/docs/math.html @@ -152,8 +152,8 @@ 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 => 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/checkProp.md b/snippets/checkProp.md index af0f5bdd0..190add9fb 100644 --- a/snippets/checkProp.md +++ b/snippets/checkProp.md @@ -25,6 +25,7 @@ const checkProp = (predicate, prop) => obj => !!predicate(obj[prop]); + const lengthIs4 = checkProp(l => l === 4, 'length'); lengthIs4([]); // false lengthIs4([1,2,3,4]); // true diff --git a/snippets/factorial.md b/snippets/factorial.md index cf3acc9cc..86ebe69b6 100644 --- a/snippets/factorial.md +++ b/snippets/factorial.md @@ -11,8 +11,8 @@ 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/snippets/pipeAsyncFunctions.md b/snippets/pipeAsyncFunctions.md index 47d6f620c..8c93add3b 100644 --- a/snippets/pipeAsyncFunctions.md +++ b/snippets/pipeAsyncFunctions.md @@ -17,7 +17,7 @@ const sum = pipeAsyncFunctions( 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 58de9c2e0..a8c472774 100644 --- a/snippets/remove.md +++ b/snippets/remove.md @@ -9,9 +9,9 @@ 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); + }, []) : []; ``` diff --git a/test/_30s.js b/test/_30s.js index 2c0a2ba21..aa7470720 100644 --- a/test/_30s.js +++ b/test/_30s.js @@ -347,8 +347,8 @@ const extendHex = shortHex => 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); @@ -1004,9 +1004,9 @@ 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) =>