diff --git a/README.md b/README.md index e165c6361..1e8ec7625 100644 --- a/README.md +++ b/README.md @@ -267,6 +267,7 @@ average(1, 2, 3); * [`times`](#times) * [`uncurry`](#uncurry) * [`unfold`](#unfold) +* [`when`](#when) @@ -4694,6 +4695,30 @@ unfold(f, 10); // [-10, -20, -30, -40, -50]
[⬆ Back to top](#table-of-contents) + +### when + +Tests a value, `x`, against a predicate function. If `true`, return `fn(x)`. Else, return `x`. + +Return a function expecting a single value, `x`, that returns the appropriate value based on `pred`. + +```js +const when = (pred, whenTrue) => x => (pred(x) ? whenTrue(x) : x); +``` + +
+Examples + +```js +const doubleEvenNumbers = when(x => x % 2 === 0, x => x * 2); +doubleEvenNumbers(2); // 4 +doubleEvenNumbers(1); // 1 +``` + +
+ +
[⬆ Back to top](#table-of-contents) + --- ## ➗ Math diff --git a/docs/adapter.html b/docs/adapter.html index 192809bd2..87b13a3de 100644 --- a/docs/adapter.html +++ b/docs/adapter.html @@ -79,7 +79,7 @@ document.getElementById('doc-drawer-checkbox').checked = false; } }, false); - }

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Adapter

ary

Creates a function that accepts up to n arguments, ignoring any additional arguments.

Call the provided function, fn, with up to n arguments, using Array.slice(0,n) and the spread operator (...).

const ary = (fn, n) => (...args) => fn(...args.slice(0, n));
+      }
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Adapter
ary
Creates a function that accepts up to n arguments, ignoring any additional arguments.
Call the provided function, fn, with up to n arguments, using Array.slice(0,n) and the spread operator (...).
const ary = (fn, n) => (...args) => fn(...args.slice(0, n));
 
const firstTwoMax = ary(Math.max, 2);
 [[2, 6, 'a'], [8, 4, 6], [10]].map(x => firstTwoMax(...x)); // [6, 8, 10]
 
call
Given a key and a set of arguments, call them when given a context. Primarily useful in composition.
Use a closure to call a stored key with stored arguments.
const call = (key, ...args) => context => context[key](...args);
diff --git a/docs/array.html b/docs/array.html
index 4275f4276..042200070 100644
--- a/docs/array.html
+++ b/docs/array.html
@@ -79,7 +79,7 @@
             document.getElementById('doc-drawer-checkbox').checked = false;
           }
         }, false);
-      }
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Array
all
Returns true if the provided predicate function returns true for all elements in a collection, false otherwise.
Use Array.every() to test if all elements in the collection return true based on fn. Omit the second argument, fn, to use Boolean as a default.
const all = (arr, fn = Boolean) => arr.every(fn);
+      }
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Array
all
Returns true if the provided predicate function returns true for all elements in a collection, false otherwise.
Use Array.every() to test if all elements in the collection return true based on fn. Omit the second argument, fn, to use Boolean as a default.
const all = (arr, fn = Boolean) => arr.every(fn);
 
all([4, 2, 3], x => x > 1); // true
 all([1, 2, 3]); // true
 
any
Returns true if the provided predicate function returns true for at least one element in a collection, false otherwise.
Use Array.some() to test if any elements in the collection return true based on fn. Omit the second argument, fn, to use Boolean as a default.
const any = (arr, fn = Boolean) => arr.some(fn);
diff --git a/docs/browser.html b/docs/browser.html
index f31071fa8..218af59d5 100644
--- a/docs/browser.html
+++ b/docs/browser.html
@@ -79,7 +79,7 @@
             document.getElementById('doc-drawer-checkbox').checked = false;
           }
         }, false);
-      }
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Browser
arrayToHtmlList
Converts the given array elements into <li> tags and appends them to the list of the given id.
Use Array.map() and document.querySelector() to create a list of html tags.
const arrayToHtmlList = (arr, listID) =>
+      }
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Browser
arrayToHtmlList
Converts the given array elements into <li> tags and appends them to the list of the given id.
Use Array.map() and document.querySelector() to create a list of html tags.
const arrayToHtmlList = (arr, listID) =>
   arr.map(item => (document.querySelector('#' + listID).innerHTML += `<li>${item}</li>`));
 
arrayToHtmlList(['item 1', 'item 2'], 'myListID');
 
bottomVisible
Returns true if the bottom of the page is visible, false otherwise.
Use scrollY, scrollHeight and clientHeight to determine if the bottom of the page is visible.
const bottomVisible = () =>
diff --git a/docs/date.html b/docs/date.html
index 541993c59..055440ea7 100644
--- a/docs/date.html
+++ b/docs/date.html
@@ -79,7 +79,7 @@
             document.getElementById('doc-drawer-checkbox').checked = false;
           }
         }, false);
-      }
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Date
formatDuration
Returns the human readable format of the given number of milliseconds.
Divide ms with the appropriate values to obtain the appropriate values for day, hour, minute, second and millisecond. Use Object.entries() with Array.filter() to keep only non-zero values. Use Array.map() to create the string for each value, pluralizing appropriately. Use String.join(', ') to combine the values into a string.
const formatDuration = ms => {
+      }
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Date
formatDuration
Returns the human readable format of the given number of milliseconds.
Divide ms with the appropriate values to obtain the appropriate values for day, hour, minute, second and millisecond. Use Object.entries() with Array.filter() to keep only non-zero values. Use Array.map() to create the string for each value, pluralizing appropriately. Use String.join(', ') to combine the values into a string.
const formatDuration = ms => {
   if (ms < 0) ms = -ms;
   const time = {
     day: Math.floor(ms / 86400000),
diff --git a/docs/function.html b/docs/function.html
index f4a7c9b0a..a8c9b5f23 100644
--- a/docs/function.html
+++ b/docs/function.html
@@ -79,7 +79,7 @@
             document.getElementById('doc-drawer-checkbox').checked = false;
           }
         }, false);
-      }
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Function
attempt
Attempts to invoke a function with the provided arguments, returning either the result or the caught error object.
Use a try... catch block to return either the result of the function or an appropriate error.
const attempt = (fn, ...args) => {
+      }
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Function
attempt
Attempts to invoke a function with the provided arguments, returning either the result or the caught error object.
Use a try... catch block to return either the result of the function or an appropriate error.
const attempt = (fn, ...args) => {
   try {
     return fn(...args);
   } catch (e) {
@@ -293,4 +293,8 @@ console.log<
 };
 
var f = n => (n > 50 ? false : [-n, n + 10]);
 unfold(f, 10); // [-10, -20, -30, -40, -50]
+
when
Tests a value, x, against a predicate function. If true, return fn(x). Else, return x.
Return a function expecting a single value, x, that returns the appropriate value based on pred.
const when = (pred, whenTrue) => x => (pred(x) ? whenTrue(x) : x);
+
const doubleEvenNumbers = when(x => x % 2 === 0, x => x * 2);
+doubleEvenNumbers(2); // 4
+doubleEvenNumbers(1); // 1
 

\ No newline at end of file
diff --git a/docs/math.html b/docs/math.html
index 54fc48d9d..b7c35ed11 100644
--- a/docs/math.html
+++ b/docs/math.html
@@ -79,7 +79,7 @@
             document.getElementById('doc-drawer-checkbox').checked = false;
           }
         }, false);
-      }
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Math
approximatelyEqual
Checks if two numbers are approximately equal to each other.
Use Math.abs() to compare the absolute difference of the two values to epsilon. Omit the third parameter, epsilon, to use a default value of 0.001.
const approximatelyEqual = (v1, v2, epsilon = 0.001) => Math.abs(v1 - v2) < epsilon;
+      }
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Math
approximatelyEqual
Checks if two numbers are approximately equal to each other.
Use Math.abs() to compare the absolute difference of the two values to epsilon. Omit the third parameter, epsilon, to use a default value of 0.001.
const approximatelyEqual = (v1, v2, epsilon = 0.001) => Math.abs(v1 - v2) < epsilon;
 
approximatelyEqual(Math.PI / 2.0, 1.5708); // true
 
average
Returns the average of two or more numbers.
Use Array.reduce() to add each value to an accumulator, initialized with a value of 0, divide by the length of the array.
const average = (...nums) => [...nums].reduce((acc, val) => acc + val, 0) / nums.length;
 
average(...[1, 2, 3]); // 2
diff --git a/docs/node.html b/docs/node.html
index 76e8b0552..dd2c2a1bd 100644
--- a/docs/node.html
+++ b/docs/node.html
@@ -79,7 +79,7 @@
             document.getElementById('doc-drawer-checkbox').checked = false;
           }
         }, false);
-      }
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Node
atob
Decodes a string of data which has been encoded using base-64 encoding.
Create a Buffer for the given string with base-64 encoding and use Buffer.toString('binary') to return the decoded string.
const atob = str => new Buffer(str, 'base64').toString('binary');
+      }
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Node
atob
Decodes a string of data which has been encoded using base-64 encoding.
Create a Buffer for the given string with base-64 encoding and use Buffer.toString('binary') to return the decoded string.
const atob = str => new Buffer(str, 'base64').toString('binary');
 
atob('Zm9vYmFy'); // 'foobar'
 
btoa
Creates a base-64 encoded ASCII string from a String object in which each character in the string is treated as a byte of binary data.
Create a Buffer for the given string with binary encoding and use Buffer.toString('base64') to return the encoded string.
const btoa = str => new Buffer(str, 'binary').toString('base64');
 
btoa('foobar'); // 'Zm9vYmFy'
diff --git a/docs/object.html b/docs/object.html
index 528ebee1a..b5760e268 100644
--- a/docs/object.html
+++ b/docs/object.html
@@ -79,7 +79,7 @@
             document.getElementById('doc-drawer-checkbox').checked = false;
           }
         }, false);
-      }
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Object
bindAll
Binds methods of an object to the object itself, overwriting the existing method.
Use Array.forEach() to return a function that uses Function.apply() to apply the given context (obj) to fn for each function specified.
const bindAll = (obj, ...fns) =>
+      }
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Object
bindAll
Binds methods of an object to the object itself, overwriting the existing method.
Use Array.forEach() to return a function that uses Function.apply() to apply the given context (obj) to fn for each function specified.
const bindAll = (obj, ...fns) =>
   fns.forEach(
     fn => (
       (f = obj[fn]),
diff --git a/docs/string.html b/docs/string.html
index ae2cc0a96..5978a0e16 100644
--- a/docs/string.html
+++ b/docs/string.html
@@ -79,7 +79,7 @@
             document.getElementById('doc-drawer-checkbox').checked = false;
           }
         }, false);
-      }
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String
byteSize
Returns the length of a string in bytes.
Convert a given string to a Blob Object and find its size.
const byteSize = str => new Blob([str]).size;
+      }
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String
byteSize
Returns the length of a string in bytes.
Convert a given string to a Blob Object and find its size.
const byteSize = str => new Blob([str]).size;
 
byteSize('😀'); // 4
 byteSize('Hello World'); // 11
 
capitalize
Capitalizes the first letter of a string.
Use array destructuring and String.toUpperCase() to capitalize first letter, ...rest to get array of characters after first letter and then Array.join('') to make it a string again. Omit the lowerRest parameter to keep the rest of the string intact, or set it to true to convert to lowercase.
const capitalize = ([first, ...rest], lowerRest = false) =>
diff --git a/docs/type.html b/docs/type.html
index 3c8527a65..b916ad96b 100644
--- a/docs/type.html
+++ b/docs/type.html
@@ -79,7 +79,7 @@
             document.getElementById('doc-drawer-checkbox').checked = false;
           }
         }, false);
-      }
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Type
getType
Returns the native type of a value.
Returns lowercased constructor name of value, "undefined" or "null" if value is undefined or null.
const getType = v =>
+      }
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Type
getType
Returns the native type of a value.
Returns lowercased constructor name of value, "undefined" or "null" if value is undefined or null.
const getType = v =>
   v === undefined ? 'undefined' : v === null ? 'null' : v.constructor.name.toLowerCase();
 
getType(new Set([1, 2, 3])); // 'set'
 
is
Checks if the provided value is of the specified type.
Ensure the value is not undefined or null using Array.includes(), and compare the constructor property on the value with type to check if the provided value is of the specified type.
const is = (type, val) => ![, null].includes(val) && val.constructor === type;
diff --git a/docs/utility.html b/docs/utility.html
index 76ee9ad76..ff5f1cddf 100644
--- a/docs/utility.html
+++ b/docs/utility.html
@@ -79,7 +79,7 @@
             document.getElementById('doc-drawer-checkbox').checked = false;
           }
         }, false);
-      }
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Utility
castArray
Casts the provided value as an array if it's not one.
Use Array.isArray() to determine if val is an array and return it as-is or encapsulated in an array accordingly.
const castArray = val => (Array.isArray(val) ? val : [val]);
+      }
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Utility
castArray
Casts the provided value as an array if it's not one.
Use Array.isArray() to determine if val is an array and return it as-is or encapsulated in an array accordingly.
const castArray = val => (Array.isArray(val) ? val : [val]);
 
castArray('foo'); // ['foo']
 castArray([1]); // [1]
 
cloneRegExp
Clones a regular expression.
Use new RegExp(), RegExp.source and RegExp.flags to clone the given regular expression.
const cloneRegExp = regExp => new RegExp(regExp.source, regExp.flags);
diff --git a/snippets/when.md b/snippets/when.md
index 3ad0ceab7..b16c7ff32 100644
--- a/snippets/when.md
+++ b/snippets/when.md
@@ -5,14 +5,11 @@ Tests a value, `x`, against a predicate function. If `true`, return `fn(x)`. Els
 Return a function expecting a single value, `x`, that returns the appropriate value based on `pred`.
 
 ```js
-const when = (pred, whenTrue) => (x) => pred(x) ? whenTrue(x) : x;
+const when = (pred, whenTrue) => x => (pred(x) ? whenTrue(x) : x);
 ```
 
 ```js
-const doubleEvenNumbers = when(
-  (x) => x % 2 === 0,
-  (x) => x * 2
-);
+const doubleEvenNumbers = when(x => x % 2 === 0, x => x * 2);
 doubleEvenNumbers(2); // 4
 doubleEvenNumbers(1); // 1
 ```