diff --git a/README.md b/README.md index e1a4779c6..cdfe87fdd 100644 --- a/README.md +++ b/README.md @@ -86,6 +86,7 @@ average(1, 2, 3); * [`pipeAsyncFunctions`](#pipeasyncfunctions) * [`pipeFunctions`](#pipefunctions) * [`promisify`](#promisify) +* [`rearg`](#rearg) * [`spreadOver`](#spreadover) * [`unary`](#unary) @@ -672,6 +673,40 @@ delay(2000).then(() => console.log('Hi!')); // // Promise resolves after 2s
[⬆ Back to top](#table-of-contents) +### rearg + +Creates a function that invokes the provided function with its arguments arranged according to the specified indexes. + +Use `Array.reduce()` and `Array.indexOf()` to reorder arguments based on `indexes` in combination with the spread operator (`...`) to pass the transformed arguments to `fn`. + +```js +const rearg = (fn, indexes) => (...args) => + fn( + ...args.reduce( + (acc, val, i) => ((acc[indexes.indexOf(i)] = val), acc), + Array.from({ length: indexes.length }) + ) + ); +``` + +
+Examples + +```js +var rearged = rearg( + function(a, b, c) { + return [a, b, c]; + }, + [2, 0, 1] +); +rearged('b', 'c', 'a'); // ['a', 'b', 'c'] +``` + +
+ +
[⬆ Back to top](#table-of-contents) + + ### spreadOver Takes a variadic function and returns a closure that accepts an array of arguments to map to the inputs of the function. diff --git a/docs/index.html b/docs/index.html index ca0cc9869..c29967d9b 100644 --- a/docs/index.html +++ b/docs/index.html @@ -50,7 +50,7 @@ scrollToTop(); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.

 

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));
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.
 
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);
@@ -107,6 +107,20 @@ Object.assig
   );
 
const delay = promisify((d, cb) => setTimeout(cb, d));
 delay(2000).then(() => console.log('Hi!')); // // Promise resolves after 2s
+
rearg
Creates a function that invokes the provided function with its arguments arranged according to the specified indexes.
Use Array.reduce() and Array.indexOf() to reorder arguments based on indexes in combination with the spread operator (...) to pass the transformed arguments to fn.
const rearg = (fn, indexes) => (...args) =>
+  fn(
+    ...args.reduce(
+      (acc, val, i) => ((acc[indexes.indexOf(i)] = val), acc),
+      Array.from({ length: indexes.length })
+    )
+  );
+
var rearged = rearg(
+  function(a, b, c) {
+    return [a, b, c];
+  },
+  [2, 0, 1]
+);
+rearged('b', 'c', 'a'); // ['a', 'b', 'c']
 
spreadOver
Takes a variadic function and returns a closure that accepts an array of arguments to map to the inputs of the function.
Use closures and the spread operator (...) to map the array of arguments to the inputs of the function.
const spreadOver = fn => argsArr => fn(...argsArr);
 
const arrayMax = spreadOver(Math.max);
 arrayMax([1, 2, 3]); // 3