Add pipeAsyncFunctions

snippets/pipeAsyncFunctions.md

@@ -0,0 +1,22 @@
+### pipeAsyncFunctions
+
+Performs left-to-right function composition.
+
+Use `Array.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.
+
+```js
+const pipeAsyncFunctions = (...fns) => arg => fns.reduce((p, f) => p.then(f), Promise.resolve(arg));
+```
+
+```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 () => {
+  console.log(await sum(5)); // 15 (after one second)
+})();
+```

tag_database

@@ -169,6 +169,7 @@ partition:array,object,function
 percentile:math
 pick:object,array
 pickBy:object,array,function
+pipeAsyncFunctions:adapter,function,async
 pipeFunctions:adapter,function
 pluralize:string
 powerset:math

test/pipeAsyncFunctions/pipeAsyncFunctions.js

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+const pipeAsyncFunctions = (...fns) => arg => fns.reduce((p, f) => p.then(f), Promise.resolve(arg));
+module.exports = pipeAsyncFunctions

test/pipeAsyncFunctions/pipeAsyncFunctions.test.js

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+const test = require('tape');
+const pipeAsyncFunctions = require('./pipeAsyncFunctions.js');
+
+test('Testing pipeAsyncFunctions', async (t) => {
+  //For more information on all the methods supported by tape
+  //Please go to https://github.com/substack/tape
+  t.true(typeof pipeAsyncFunctions === 'function', 'pipeAsyncFunctions is a Function');
+  //t.deepEqual(pipeAsyncFunctions(args..), 'Expected');
+  //t.equal(pipeAsyncFunctions(args..), 'Expected');
+  //t.false(pipeAsyncFunctions(args..), 'Expected');
+  //t.throws(pipeAsyncFunctions(args..), 'Expected');
+  t.equal(
+    await pipeAsyncFunctions(
+      (x) => x + 1,
+      (x) => new Promise((resolve) => setTimeout(() => resolve(x + 2), 0)),
+      (x) => x + 3,
+      async (x) => await x + 4,
+    )
+    (5),
+    15,
+    'pipeAsyncFunctions result should be 15'
+  );
+  t.end();
+});